Amorphous Composites Research Articles

Cu Nanoclusters/FeN4 Amorphous Composites with Dual Active Sites in N-Doped Graphene for High-Performance Zn-Air Batteries.

Exploring inexpensive and earth-abundant transition metal-nitrogen-based carbon (MNC) catalysts to substitute the scarce and costly Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is quite anticipated in metal-air batteries (MABs). Here, we demonstrate a facile vacuum-annealing method to synthesize Cu nanoclusters/FeN4 amorphous composites embedded in N-doped graphene (Cu/Fe-NG). This approach avoids the long-term pyrolysis procedure and the use of an inert atmosphere in the conventional procedure for fabricating MNC catalysts. Interestingly, we discovered that the amorphous structure of Cu/FeN4 composites can provide high-activity bimetallic M-Nx sites (M = Cu, Fe), because of which the Cu/FeN4 composites exhibit boosted electrocatalytic activity with a positive half-wave potential of 0.88 V (vs RHE), long-term durability, and low hydrogen peroxide for the ORR. The origin of this enhancement was assigned to the concomitance of Fe-N4 and Cu-Nx moieties in Cu/Fe-NG, favoring adsorption and activation of the O2 molecule as suggested by X-ray absorption fine structure (XAFS) analyses and density functional theory (DFT) calculations. Moreover, examinations of Cu/Fe-NG in both liquid and quasi-solid-state Zn-air batteries (ZABs) can exhibit remarkable performances. This work may offer facile fabrication of enhanced performance MNC catalysts as well as a profound insight into the use of amorphous materials in the ORR and ZABs.

High-entropy alloy and amorphous alloy composites fabricated by ultrasonic vibrations

We successfully fabricate high-entropy alloys and amorphous alloy composites by adopting the proposed ultrasonic vibration method. The low-stress, low-temperature method enables us to create composites that combine both amorphous and crystalline properties. Microscopic observations and computed tomography measurements indicate good bonding quality without pores or cracks in the composites. Due to the unique structure which mixes soft and rigid phases, the composite exhibits improved mechanical performance compared to that obtained from a pure single phase. Our results are promising for the manual design and fabrication of smart materials containing multiple phases and compositions.

Modification of the Electronic Transport By Liquid Electrolytes in Mixtures Based on LiNi0.5Mn0.3Co0.2O2 and Polyvinylidene Fluoride

The electrochemical performance of composite electrode materials suffers strong kinetic limitations due to non-optimized electronic and ionic transport properties. Electrode materials consist of complex hierarchical architectures in which interfaces create junction resistances and capacitance causing electronic transfer limitations. Moreover, the tortuosity of the pore network within the electrodes gives rise to ionic transfer limitations. Ionic and electronic dynamics occur at widely different time scales: long times (i.e. low frequencies) for slow ionic motions and short times (i.e. high frequencies) for fast electronic motions. Electrochemical Impedance Spectroscopy technique, which is appropriated to determine ionic diffusion, cannot characterize electronic transfers within electrode materials. This requires thus the simultaneous measurement of ionic and electronic conductivities. The broadband dielectric spectroscopy (BDS) over a frequency range from 40 Hz to 10 GHz is a powerful technique to discriminate ionic and electronic motions at different scales of the materials.Previous BDS studies have distinguished different types of interfaces inducing electric polarizations and disturbing charge transport at all scales of the materials [1-5]. Strong interactions between ions (Li+, PF6 - ) of the electrolyte (LP30) and electrons were evidenced in active material (LiNi1/3Mn1/3Co1/3O2) and carbon black (CB) by conductivity measurements.Comprehensive characterization of the multiscale electronic transport in LiNi0.5Mn0.3Co0.2O2 (hereafter called NMC532) by BDS is here detailed. This study is assumed without carbon-black addition to only understand the interactions of the electrolyte with mixtures based on NMC532 and PVdF. A systematic approach is followed, which consists of studying the materials at different temperatures, starting by a study of NMC532 with polyvinylidene fluoride (i.e. PVdF) first in the dry state, then filled with the solvent EC-DMC alone and finally the LP30 electrolyte (containing ions).The PVdF content impacts the quality of the interfaces within the samples hampering the electronic transfer in NMC. When EC: DMC fills the pores of the mixture, it is shown that the dipoles of ethylene carbonate adsorbed on the NMC532 modify its electronic properties.Moreover, strong interactions occur between the liquid electrolyte LP30 (i.e. dipoles and ions) and the active material, as well as between the electrolyte and the carbon black. Space charges, created on the surface of electronically conductive NMC532 generate electrical polarizations whose frequency responses are in the range of radio frequencies and microwaves. The presence of the electrolyte changes the intensities and dynamics of space charge polarizations due to ion-electron and dipole-electron interactions [3,4]. Acknowledgments Financial funding from the ANR program no. ANR-15-CE05-0001-01 is acknowledged References [1] K.A. Seid, J.C. Badot, O. Dubrunfaut, S. Levasseur, D. Guyomard, B. Lestriez, Multiscale electronic transport mechanism and true conductivities in amorphous carbon-LiFePO4 composites. J. Mater. Chem., 22, 2641-2649 (2012). [2] K.A. Seid, J.C. Badot, O. Dubrunfaut, M.T. Caldes, N. Stephant, L. Gautier, D. Guyomard, B. Lestriez, Multiscale electronic transport in Li1+xNi1/3-uCo1/3-vMn1/3-wO2: a broadband dielectric study from 40 Hz to 10 GHz. Phys. Chem. Chem. Phys., 15, 19790-19798 (2013).[3] K.A. Seid, J.C. Badot, C. Perca, O. Dubrunfaut , P. Soudan , D. Guyomard, B. Lestriez, An In Situ Multiscale Study of Ion and Electron Motion in a Lithium-Ion Battery Composite Electrode. Adv. Energy Mater., 5, 1400903 (2015). [4] E. Panabière, J.C. Badot, O. Dubrunfaut, A. Etiemble, B. Lestriez. Electronic and Ionic Dynamics Coupled at Solid-Liquid Electrolyte Interfaces in Porous Nanocomposites of Carbon Black, Poly(vinylidene fluoride), and g-Alumina. J. Phys. Chem. C, 121, 8364-8377 (2017).[5] P.E. Cabelguen, D. Peralta, M. Cugnet, J.C. Badot, O. Dubrunfaut, P. Mailley. Rational Analysis of Layered Oxide Power Performance Limitations in a Lithium Battery Application. Adv. Sustainable Syst., DOI: 10.1002/adsu.201700078 (2017).

Tensorial description of the plasticity of amorphous composites.

We use a continuous mesoscopic model to address the yielding properties of plastic composites, formed by a host material and inclusions with different elastic and/or plastic properties. We investigate the flow properties of the composed material under a uniform externally applied deviatoric stress. We show that due to the heterogeneities induced by the inclusions, a scalar modeling in terms of a single deviatoric strain of the same symmetry as the externally applied deformation gives inaccurate results. A realistic modeling must include all possible shear deformations. Implementing this model in a two-dimensional system, we show that the effect of harder inclusions is very weak to relatively high concentrations. For softer inclusions instead, the effect is much stronger; even a small concentration of inclusions affecting the form of the flow curve and the critical stress. We also present the details of a full three-dimensional simulation scheme and obtain the corresponding results for harder and softer inclusions.

Industry-oriented Fe-based amorphous soft magnetic composites with SiO2-coated layer by one-pot high-efficient synthesis method

A new one-pot highly efficient synthesis method implemented using an industry-oriented roboticized coating device was designed and developed for obtaining high quality SiO2-coating on the surface of commrercial Fe78Si13B9 (FeSiB) amorphous flaky powder at the room temperature. Hereinto, the conventional instilling method was modified as directly pouring the ultra-diluted precursor by anhydrous ethanol into the reaction mixture, favorable for both simple operation and shortening the total manufacture time to 1.9 h (including the drying time of about 0.7 h). Comparison and analysis on the soft magnetic properties of the FeSiB amorphous powder cores insulated using different precursor concentration within the range of 0 ~ 0.25 ml/g were investigated in detail. SEM, EDS, and FTIR were employed to characterize the core-shell structure of magnetic powders. The increment of pinning sites induced by the raising precursor concentration can cause a reduction in effective permeability, while result in the increases of hysteresis loss and excess loss. The eddy current loss contributes only about 13.5% ~ 18.1% of total core loss for the coated powder cores under the TEOS concentration over 0.09 ml/g, indicating that the corresponding magnetic composites have a good electro-insulating layer. This work offered a referable idea for efficiently coating other inorganic insulations on the magnetic powders within different shapes.

Enhancing High-Temperature Strength and Thermal Stability of Al2O3/Al Composites by High-Temperature Pre-treatment of Ultrafine Al Powders

Amorphous Al2O3-reinforced Al composite (am-Al2O3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al2O3 at high temperatures will result in serious strength loss. Aiming at this unsolved problem, in this study, high-temperature Al materials with enhanced thermal stability were developed through introducing more thermally stable nano-sized particles via high-temperature pre-treatment of ultrafine Al powders. It was found that the pre-treatment at ≤ 550 °C could introduce a few Al2O3 in the Al matrix and increase the strength of the composites, but the strength was still below that of am-Al2O3/Al because without being pinned firmly, grain boundaries (GBs) were softened at high temperature and intergranular fracture happened. When the pre-treatment was carried out at 600 °C, nitridation and oxidation processes happened simultaneously, producing large numbers of intergranular (AlN + γ-Al2O3) particles. GB sliding and intergranular fracture were suppressed; therefore, higher strength than that of am-Al2O3/Al was realized. Furthermore, the (AlN + γ-Al2O3)/Al exhibited more superior thermal stability compared to am-Al2O3/Al for annealing treatment at 580 °C for 8 h. Therefore, an effective way to fabricate high-temperature Al composite with enhanced thermal stability was developed in this study.

Deformation field evolution and shear banding of an <italic>in-situ</italic> crystal reinforced amorphous alloy composite

The strain field and shear band behaviors of an in - situ crystal reinfored amorphous alloy composite at microscale were experimentally characterized by digital image correlation method. Combined with the finite element analysis, the deformation of the amorphous alloy composite was simulated, and the evolution of stress and strain fields was given out. The role of each phase during the deformation was analysed. The results show that in the macroscopically elastic range, the crystal phase first deformed plastically, then strain concentration formed at the phase interface, and gradually expanded to the surrounding. As the applied strain increased, strain localization occured inside the material. It is found that, the plastic deformation of the composites is accommodated by shear bands, and the presence of crystal phase in the amorphous alloy composite promotes the formation of multiple shear bands. The load of the composite is mainly sustained by the continuous amorphous matrix, and the shear band forms along with a rapid increase of free volume, which leads to a decrease of flow stress and subsequent a reduced loadbearing capacity of the composite.

Length scale dependent plasticity of amorphous/amorphous NiNb/ZrCuNiALSI nanolaminates

Individual layer thickness dependent mechanical properties of amorphous/amorphous NiNb/ZrCuNiAlSi nanolaminates were evaluated via nanoindentation testing. While hardness only slightly increases, the magnitude of pile-up around residual indentation was estimated to be effectively decreased at reduced individual layer thickness. By ruling out the effect of the ratio of effective elastic modulus over yield strength of the multilayers, the variation trend of pile-up may attribute to the high capacity of work hardening derived from decreasing the layer thickness. The mechanism behind the enhanced work hardening of the amorphous composites was proposed, and may path a new way to fabricate metallic glasses with improved plasticity.

Development of in-situ hybrid phase reinforced Mg-based metallic glass matrix composites

The in-situ NiTi(Nb)+β-Nb hybrid reinforcing structures have been successfully induced in a Mg-based amorphous matrix by using the novel selective phase leaching process. The size of secondary phase can be refined by increasing the cooling rate of the pre-alloys and the hybrid structure can be obtained by as-followed annealing treatment. The fracture strength of the composite improved to over 1 GPa and the plastic strain to over 13%. The ductile secondary phase is found to be effective in hindering the rapid propagation of main shear bands and contribute to the generation of multiple shear bands. The fine size of secondary phase is very close to the processing zone size of the matrix, which should further improve the interactions between the reinforcing phases and the matrix. The hybrid structure can induce a more complex stress field during deformation and may lead a breakthrough in designing the amorphous matrix composites.

Fe-based amorphous soft magnetic composites with SiO2 insulation coatings: A study on coatings thickness, microstructure and magnetic properties

Core-shell structured FeSiBCCr@SiO2 amorphous soft magnetic composites (ASMCs) with tunable insulating layer thicknesses have been designed and fabricated by the powder metallurgy method. The growth process of the coatings obtained via the sol-gel method has been systematically studied based on the analysis of the growth mechanism and the insulating layer thicknesses calculated by a modified method. In the powder-coating process using small quantities of tetraethyl orthosilicate (TEOS) (0.025–0.1 mL/g), a relatively uniform insulating layer is formed on the surface of the powders. Increasing the TEOS concentration further (0.25–1 mL/g) greatly enhances the reaction kinetics of the hydrolysis and condensation reactions. Consequently, the SiO2 shells of the amorphous powder rapidly grow in thickness and also generate aggregates. The evolution of the thickness of the coatings under different growth conditions also corresponds to the variation of the magnetic performance of the ASMCs. The ASMCs with an appropriate SiO2 insulating layer exhibit stability at high frequencies and significantly lower the contribution of eddy current to the total loss. Conversely, a thick insulation layer results in a high fraction of the non-magnetic phase and consequently enhances the hysteresis loss. Thus, an enhanced magnetic performance of the FeSiBCCr ASMCs can be achieved by adjusting the TEOS concentration (0.025–0.1 mL/g) or the thickness of the SiO2 insulating layer.

FT-IR Characterization of Antimicrobial Hybrid Materials through Sol-Gel Synthesis

Silica/polycaprolactone and titania/polycaprolactone hybrid organic/inorganic amorphous composites were prepared via a sol-gel method starting from a multi-element solution containing tetramethyl orthosilicate (TMOS) or titanium butoxide (TBT), polycaprolactone (PCL), water and methylethylketone (MEK). The molecular structure of the crosslinked network was based on the presence of the hydrogen bonds between organic/inorganic elements as confirmed by Fourier Transform Infra-Red (FT-IR) analysis. In particular, the structure of crosslinked network was realized by hydrogen bonds between the X-OH (X = Si or Ti) group (H donator) in the sol-gel intermediate species and ester groups (H-acceptors) in the repeating units of the polymer. The morphology of the hybrid materials; pore size distribution, elemental homogeneity and surface features, was studied by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and by atomic force microscopy (AFM). The bioactivity of the synthesized hybrid materials was confirmed by observing the formation of a layer of hydroxyapatite (HAP) on the surface of the samples soaked in a simulated body fluid. The antimicrobial behavior of synthetized hybrids was also assessed against Escherichia coli bacteria. In conclusion, the prepared hybrid materials are proposed for use as future bone implants.

Reactive Spark Plasma Synthesis of Porous Bioceramic Wollastonite

A method was proposed for reactive spark plasma synthesis (R-SPS) of a porous (Ssp = 12.7–8.56 m2/g) and structurally strong (σcomp = 201.1–393.2 MPa) bioceramic composite material based on wollastonite (CaSiO3) containing 20 wt % hydroxyapatite (HAP). In this method, the precursor is an amorphous composite that is based on a mixture of xonotlite (Ca6Si6O17 · 2OH) with HAP and a pore-forming agent and is prepared by the sol–gel (template) synthesis. The originality of the method consists in the formation of crystalline ceramic wollastonite by the transformation of its hydrated form, xonotlite, under spark plasma heating conditions. The densification dynamics, phase formation, and microstructural changes of the formed CaSiO3/HAP ceramic at various (500–900°C) R-SPS temperatures were studied by XRD, TGA/DTA, SEM, BET method, and porosimetry. Microbiological evaluation of the efficiency of the formation of Pseudomonas aeruginosa bacterial films on the surface of samples of the produced CaSiO3/HAP ceramic was performed, in particular, in comparison with a noncomposite material in the absence of HAP. The proposed R-SPS method ensures the creation of a porous, structurally strong composite ceramic containing a biocompatible component (HAP). This ceramic can be promising for producing ceramic bone implants for bone defect restoration.

Effects of strain rate on the tensile behavior of cementitious composites made with amorphous metallic fiber

Amorphous metallic fiber has higher tensile strength as well as corrosion and wear resistance than common, crystalline steel fibers. Its utilization as reinforcement improves the crack resistance and flexural and tensile performance of concrete. In the study at hand, the tensile behavior of thin plate amorphous metallic fiber-reinforced cementitious composites (AFRCC) is compared with that of hooked steel fiber-reinforced cementitious composites (HSFRCC) for both quasi-static and dynamic loading regimes. AFRCC exhibites a high stress distribution effect and higher tensile strength, strain capacity, and peak toughness than HSFRCC, but lower tensile toughness and lower dynamic increase factor values for tensile strength, strain capacity, and toughness.

Strengthening mechanism and thermal deformation behavior of Al-12Si/Fe piston composite

The present paper aims the investigation on the influence of Fe based amorphous on strength of aluminum alloy (Al-12Si), and the thermal deformation behavior of new Al-12Si/Fe base amorphous composites. On this foundation, a heat flow stress model of the sample was proposed by a Zener-Hollomon parameter and microstructural studies were carried out on Al-12Si/Fe base amorphous composite by many means. Microstructural study reveals dynamic recovery and dynamic recrystallization of Al-12Si/Fe base amorphous composite at thermal compression text. In addition, the deformation activation energy of Al-12Si/Fe-based amorphous composites is as high as 211.29 kJ mol−1, compared with Al-12Si alloy (170.51 kJ mol−1). Importantly, the flow stress equation of the new composite is = 4.42×1014 [sinh(0.0166σ)]6.13 exp(−211290/RT), and the linear regression coefficient is 0.99. This study constitutes a significant advance in strengthening the Al-12Si engine piston and controlling the thermal deformation behavior and opens new directions for the development of piston material.

Experimental Study on Mechanical and Electrical Properties of PV‐PVC Composites

Based on BIPV, the idea of flexible amorphous silicon solar cell (PV) and PVC membrane composite was put forward. In this paper, the influence of composite mode and force form is mainly investigated. The mechanical and electrical properties of PV‐PVC composite under uniaxial and cyclic tension are obtained. The main results show that the tensile strength of PV‐PVC composite is basically the same as that of PVC membrane. Compared with PVC membrane, the modulus of elasticity of PV‐PVC composite under cyclic loading is significantly increased, while the residual strain and the area of hysteresis loop are significantly reduced. The difference in mechanical properties of different off‐axis angles is significantly reduced. Under the stress level of common design strength of PVC membrane materials, solar cells can play a good photoelectric effect. This paper provides an important reference for the realization of membrane structure photovoltaic integration.

Phytic acid controlled in situ synthesis of amorphous cobalt phosphate/carbon composite as anode materials with a high mass loading for symmetrical supercapacitor: amorphization of the electrode to boost the energy density.

Transition metal phosphate (TMPi)-based composites as anode electrode materials in supercapacitor applications are less reported. Herein, we report a phytic acid (PA)-assisted in situ-formed amorphous cobalt phosphate/carbon (CoPi/C) composite grown on a flexible woven carbon cloth (CC) via a simple one-step carbonization approach. The tunable synthesis of amorphous and crystalline composites is shown by simply controlling the concentration of the cobalt salts. The strategy for high mass loading to 12 mg cm−2 is also shown in this report. Importantly, the resulting amorphous electrode materials exhibit electric double-layer capacitance (EDLC) behavior that works over a wide potential range from −1.4 to +0.5 V in an aqueous solution of potassium hydroxide (2 M KOH) and from −1.5 to +1.5 V in sodium sulfate (1 M Na2SO4). The amorphous electrode as an anode is capable of delivering an areal capacitance up to 2.15 F cm−2 at a current density of 4 mA cm−2 (gravimetric capacitance up to 606.1 F g−1 at 1 Ag−1) and has a retention of 94.2% at 10 000 cycles. The flexible solid-state symmetric device fabricated shows an energy density of approximately 620.0 μW h cm−2 at a power density of 4.7 mW cm−2 (31.1 W h kg−1 at 476.0 W kg−1). This study offers a novel route for the generation of metal phosphate-based anode materials with high capacitance for symmetrical supercapacitor device with high energy density.

Tracking the interaction of drug molecules with individual mesoporous amorphous calcium phosphate/ATP nanocomposites – an X-ray spectromicroscopy study

Adenosine triphosphate (ATP) biomolecules play critial roles in the biomineralization process during the formation of amorphous calcium phosphate composites (ACPC), and ACPC is an important drug carrier due to its significant advantages of biocompatibility and biodegradability. Hence, studying the behavior of ACPC nanodrug carriers is crucial to investigate the structural regulation of biomimetic minerals and calcium phosphate (CaP)-based drug delivery systems. However, it is difficult to probe these interactions using traditional characterization methods. In this paper, XANES analysis together with STXM successfully provided a method to reveal the interaction of ATP and drug molecules with individual mesoporous ACPC. We found that the adenosine and phosphate groups of ATP biomolecules coordinated with Ca2+ and played critical roles in the formation of ACPC; drug molecules with the -COOH groups were linked to Ca2+via carboxylic acid groups primarily by electrostatic interactions, and the N-containing ring structures within the drug molecules also coordinated with Ca2+.

Study on microstructure and mechanical properties of Fe-based amorphous particle-reinforced Al-based matrix composites

Fe52Cr15Mo26C3B1Y3 amorphous particle-reinforced pure aluminum (Al) matrix composite was prepared by powder metallurgy. The ferrum (Fe)-based amorphous particles prepared by atomization method have good amorphous structure, and the circular reinforcement particles are evenly distributed in the Al matrix. The composite has high strength, hardness, and excellent corrosion resistance. The hardness of the composite increases gradually with the increase in the content of the reinforcement, from 46 Vickers hardness (HV) of pure Al to 220.5 HV, with remarkable effect. The tensile strength of the composite increases first and then decreases with the increase in the content of the reinforcement. When the content of reinforcement is 15%, the maximum tensile strength is 234 MPa, which is 154% higher than that of pure Al. The fracture mode of the composite is the mixture of plastic fracture and brittle fracture. The corrosion resistance of pure Al is significantly improved by the addition of reinforcements, which shows that the composite has a smaller corrosion current density and a more positive corrosion potential than that of pure Al.

Encapsulation of poorly soluble drugs in yeast glucan particles by spray drying improves dispersion and dissolution properties.

In this work, novel amorphous solid dispersions based on yeast glucan particles were produced. Yeast glucan particles are hollow and porous, and they are mainly composed of amorphous polysaccharides. We hypothesized that these particles are suitable candidates for the amorphization of drugs with low water solubility. Model drugs ibuprofen and curcumin were successfully encapsulated in glucan particles by spray drying. Different spray-drying parameters were tested to evaluate the influence of atomizing droplet size and initial solid content on encapsulation efficiency. It was shown that higher solid content and, more significantly, larger droplet sizes lead to higher encapsulation efficiencies. The encapsulation efficiency of ibuprofen (10wt%) into glucan particles was considerably improved from 41.3±0.5% to 64.3±0.2% by increasing initial solid content and droplet size with the two-fluid nozzle. The spray drying process was further optimized by using the ultrasonic nozzle and it was possible to achieve complete encapsulation of ibuprofen and curcumin without any precipitation of the active compound outside of the glucan particles. Overall, it was possible to produce completely amorphous composites with outstanding wettability and dispersion properties, and with significantly faster dissolution rates when compared to the micronized crude drug.

Antimicrobial activity and synergistic antibacterial mechanism of a combination of zinc and rare-earth scandium against Escherichia coli

ABSTRACT In this study, rare-earth elements Sc and Zn were deposited on an advanced functional antimicrobial amorphous silica composite (ASC) using the sol–gel method at room temperature. The optimal preparation conditions were determined to achieve the maximum antibacterial activity by evaluating single factors. The optimal Zn2+ and Sc3+ concentrations were found to be 0.9 mol·L–1 and 3 mmol·L–1, respectively. The results show that the Zn-Sc ASC is amorphous and porous. ICP analysis indicated 1.81% Zn and 0.058% Sc (wt%). The antibacterial activity of Zn ASC after adding rare-earth element Sc increased from 65% to 90%. The synergistic antibacterial effect between Sc and Zn ASC can be attributed to the increased specific surface area of Zn ASC owing to the addition of Sc and the enhanced loading of Zn2+ on ASC producing more reactive oxygen species (ROS).