Glassy Powders Research Articles

Iron nitride based magnetic powder synthesized by mechanical alloying of Fe-based glassy powders and solid nitrogen compounds

Iron nitrides composed of abundant and inexpensive Fe and N compounds such as α′′-Fe16N2 and γ’-Fe4N are in the spotlight as potential magnetic materials for the next generation of electric vehicles. Extensive applications of iron nitrides, however, have not been reported since their mass production is yet to be established. Due to the low solubility of nitrogen in liquid iron, the production of iron nitrides through conventional steelmaking processes is difficult. Moreover, α′′-Fe16N2 with a high saturation magnetization is known to be metastable and can form below 200 °C where diffusional phase transformations are slow. In this study, we propose a nonequilibrium process that can enhance the kinetics for iron nitride formation at low temperatures. Thermodynamically metastable Fe-based glassy alloy with a relatively open atomic packing structure was used as the starting material. Synthesis of iron nitrides during the mechanical alloying of Fe-based amorphous powders and solid nitrogen compounds was systematically studied to understand the mechanism of solid state nitriding reactions. In addition, thermal and magnetic properties were studied to provide a basis for practical applications of iron nitrides as rare-earth free magnetic materials.

General route to fabricate ultrafine metallic glass powders directly from their own crystalline states by localized pulsed electrical discharge atomization

Localized pulsed electrical discharge (PED) atomization is developed as a general route to fabricate ultrafine metallic glass powders with high purity and sphericity, which cannot be achieved by conventional techniques, like mechanical alloying, chemical reduction and water/gas atomization. The new atomization process starts with a localized melting on crystalline alloy surface by PED. During the melting process, multiple crystalline phases in the starting alloy are melted and then homogenized to form a uniform melted zone. Finally, the melted zone is atomized to produce ultrafine powders under the explosive force. The obtained particle size is mainly in the range of 1–10 μm. The results also show that it is easier to vitrify the produced powders for alloys with higher glass-forming ability (GFA). However, considering that the cooling rates achieved by PED atomization and melt-spinning technique are comparable, the GFA of the starting alloy will not play a determining role in the formation of glassy powders as long as it can guarantee the formation of glassy ribbons by melt-spinning technique. In this case, the ratio of melted zone size to crystalline phase size become the determining factor. The amorphization degree and compositional homogeneity can be improved by refining the starting alloy with low GFA. Besides, the experimental and simulation results both eliminate the possible Mo pollution from the tool electrode. This work will hopefully expand the applications of metallic glasses.

Efficient Addition of Waste Glass in MK-Based Geopolymers: Microstructure, Antibacterial and Cytotoxicity Investigation.

Reuse of waste glass can significantly decrease the quantity of waste to be treated or disposed of in landfills, allowing to both diminish the ecological damage and to reduce the costs of transportation for removal. Geopolymer mixes with diverse percentages (20, 50 and 60 wt%) and with different grain size ranges (37 μm < diam < 53 μm; 75 μm < diam < 105 μm) of waste glass and the residual part of pure metakaolin were prepared by addition of NaOH and sodium silicate as alkaline activator solutions. The effect of waste glass on the mechanical and microstructure of new geopolymers has been explored in this study. Fourier transform infrared spectroscopy (FTIR) evidenced the reactivity of waste glass in terms of Si–O and Si–O–Al bonds, more evident for the finer waste glass powder. The consolidation of the materials has been established by reduced weight loss in water and decreased pH and ionic conductivity of the eluate after 7, 14 and 28 days of curing at room temperature. The decrease of the mechanical properties with waste glass content was less evident for the finer glassy powders, yet the value of about 4-5 MPa indicates their potential use as non-structural materials. The consolidated final materials were tested for their effects on the microbial growth of Escherichia coli and Enterococcus faecalis after 24 and 48 h, respectively. The samples showed a very limited and absent inhibition zone, for fine and coarse grain size ranges, respectively. Finally, the cytotoxicity tests accomplished the ecological valuation of the final consolidated products.

Maltodextrin improves physical properties and volatile compound retention of spray-dried asparagus concentrate

Traditional hot air drying of asparagus is known to lead to a powder with a poor aroma profile. We here concentrated asparagus juice into asparagus concentrate (21.7% w/w) and spray-dried it with maltodextrin DE12 as carrier agent to improve the volatile profiles of asparagus powder and to valorise fresh asparagus side-streams. We performed headspace GC-MS with untargeted metabolomics to assess the overall metabolite profile of the spray-dried asparagus powders and identified 70 volatile compounds. The maltodextrin content was positively correlated to the retention of an asparagus key odorant 1-octen-3-ol, as well as other alcohols and aldehydes. Nevertheless, drying conditions had limited effect on the volatile retention of the powders. Moreover, higher outlet temperatures increase the presence of volatiles that were formed during drying, such as 3-methylthio-propanal. From our analyses, it was further found that an increased concentration of maltodextrin was correlated to a lower moisture content, a higher glass transition temperature (Tg) and a narrower size distribution of the spray-dried powders. The Tg of all powders was described with the Gordon-Taylor equation for multicomponent mixtures, and we found a minimum weight fraction of 0.67 (w/dw) maltodextrin required to obtain glassy asparagus powder for storing at ambient conditions.

Efficient degradation of orange II dye using Fe-based metallic glass powders prepared by commercial raw materials

An efficient, economical and reusable Fe-based metallic glass (MG) powders were prepared for degrading Orange II solution. The influence parameters such as initial pH, temperature, recycle times and initial Orange II concentration were investigated for the degradation efficiency. The experimental result shows that 98.6% degradation rate was achieved within 2 min using low dosage Fe–Si–B–P–C glassy powders at acidic pH value. In addition to the metastable properties of glassy powders, the excellent degradation performance can relate to the spongy porosity of powder surface appeared during degradation treatment. We also found that the degradation rate improved obviously with the increase of temperature or acid strength in solution. After recycle experiment of six times, the glassy powders still maintained high degradation efficiency to Orange II solution. This work will contribute to the development of cheap and high quality glassy powders with excellent ability to degrade azo dyes.

Whey proteins-folic acid complexes: Formation, isolation and bioavailability in a Lactobacillus casei model

Abstract The objective of this work was to explore the complexation of a whey protein (β-lactoglobulin, β-lg) and a whey protein isolate (WPI) with folic acid (FA) at pH 3.0. Complexes were formed through non-covalent interactions, mainly electrostatic, as showed by ƺ-potential determination. Whey protein aggregation induced by the FA linkage was achieved, with particle sizes within the nano and microscales. Particle size distribution in aqueous solution was determined by dynamic light scattering (DLS) obtaining values between 15−200 nm. Complexes isolation was achieved by spontaneous phase separation and subsequent lyophilization, obtaining a glassy powder. Particles sizes increased upon both complexation and powder rehydration. The interactions between FA and proteins were corroborated by FTIR. Confocal laser microscopy revealed the heterogeneity and extensive aggregation of the complexation.. The bioavailability of the WPI-FA and β-lg-FA complexes, evaluated by Lactobacillus casei BL23 model, was similar to that of FA alone demonstrating that these complexes can be potentially used as a new functional protein-based ingredient.

The microwave electromagnetic and absorption properties of Fe-Si-B-P-C glassy powders under chemical corrosion

The industrial pure Fe-Si-B-P-C metallic glass powders (MGPs) were found to have excellent microwave absorption properties in this paper. The effects of chemical corrosion on the electromagnetic (EM) parameters and absorption properties were investigated in great detail. After chemical corrosion with hydrochloric acid solution, a highly porous structure appeared on the surface of powders, which increased the interfacial polarization and permittivity of the MGPs. The MGPs exhibited good impedance matching and strong microwave absorption properties. When the corrosion time was 10 min at pH 3.0, the minimum reflection loss (RL) value of composites reached -68.9 dB at 8.88 GHz, where the thickness of the composites was only 2.6 mm.

Bulk metallic glass composites with high strength and electrical conductivity by sintering Cu-coated CuZrAl glassy powder

Abstract High strength and high electrical conductivity materials are the key materials for the development of modern electronic information and energy industries. In the present study, ultrahigh-strength Cu50Zr43Al7 metallic glass alloy is used as starting material. The crystalline Cu-coated Cu–Zr–Al metallic glass composite powders were prepared by the electroless copper plating of the metallic glass powders, then the composite powders were sintered by using spark plasma sintering (SPS) process. The fabricated Cu/Cu–Zr–Al bulk metallic glass composites exhibited simultaneously high strength and high electrical conductivity, as well as large plastic strain. The study opens a new way for development of new high strength and high conductivity materials.

Glass-Forming Ability and Soft Magnetic Properties of (Co75Ti25)100-xFex (x; 0-20 at.%) Systems Fabricated by SPS of Mechanically Alloyed Nanopowders.

Due to their outstanding mechanical properties and soft magnetic characteristics, cobalt-based metallic glassy alloys have stimulated much interesting research. These metastable ferromagnetic materials possess very small magnetocrystalline anisotropy, and almost zero magnetostriction. They reveal low coercivity, extremely low core loss, moderate saturation polarization, and very high magnetism. Despite these attractive physical behaviors, Co-based metallic glasses are difficult to obtain by the melting/casting and conventional rapid solidification techniques due to their poor glass-forming ability. In the present study, we succeed in preparing (Co75Ti25)100−xFex (x; 0–20 at.%) metallic glassy powders, using a mechanical alloying approach. The end product of the as-prepared powders was consolidated into full dense cylinders with large-diameter and thickness (2 × 2 cm), using spark plasma sintering technique. The results have shown that the consolidation step did not lead to any undesired crystallizations or phase transformations, and the as-consolidated buttons maintained their unique short-range order structure. These bulk metallic glassy systems possessed high glass-transition and crystallization temperatures, suggesting their high thermal stability. However, they showed low values of the reduced glass-transition temperatures, indicating that this system is difficult to prepare by the conventional way of preparations.

Optimización de las propiedades magnéticas de vidrios metálicos masivosde Zr/Fe en fase amorfa dual

The dual amorphous phase bulk metallic glasses (DAPBMGs) contain two distinct amorphous alloys in order to bring together all the favorable properties of each phase. A viable method for obtaining dual bulk amorphous alloys is powder metallurgy. A Zr/Fe DAPBMG were successfully prepared by hot-pressing of Zr –based and Fe –based glassy alloy powder in different volumetric proportions. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction. Magnetic properties were determined using hysteresis graph of integrator fluxmeter type. It was found that with increasing the volume ratio of the Fe-based alloy decreases the coercivity and increases saturation magnetization

Composite Materials Fabricated of Amorphous and Nanocrystalline Metallic Powders

The bulk metallic glasses composites are a new class of bulk metallic glasses (BMGs), containing an amorphous metal matrix and reinforcing materials of metallic or ceramic nature in order to obtaining the desired combination of mechanical properties including strength, hardness, ductility and toughness. Composite materials of cylindrical form with the diameter of 10 mm and 5 mm in height were successfully prepared by hot-pressing of Zr - based glassy alloy powder and Fe - based nanocrystalline alloy powder in different volume fraction. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction and mechanically characterized by hardness and compression tests. It was found that increasing the volume ratio of the Fe-based nanocrystalline alloy up to a certain value leads to an increase in hardness and mechanical compressive strength.

Extending the operational frequency range of high B – FeSiBP amorphous alloy to GHz by coating the powder surface with silicon oxide

Abstract We report on the fabrication, and magnetic properties of high saturation magnetic flux density (Bs) Fe76Si9B10P5 glassy alloy powder cores in which powder particles were electrically insulated by a thin layer of silicon oxide. Glassy Fe76Si9B10P5 alloy powders produced by the gas atomization technique were treated with silane coupling agent, which forms a thin silicone oxide layer on the powder surface. Toroidal shaped cores were prepared by spark plasma sintering (SPS) technique. Magnetization measurements revealed a slight decrease in the saturation magnetization from 164 emu/g (as prepared powders) to 161 emu/g after surface coating. We show that the powder surface coating is effective for decreasing the core loss at higher frequencies by suppressing the interparticle eddy currents. It is possible to have a high constant initial permeability (μi) of ~28 up to ~1.5 GHz by mixing with a small amount of resin. The constant permeability range can be extended to more than 3 GHz by completely insulating the powders electrically. Our results suggest that the metallic powder cores, which have the advantage of operating at higher Bs compared to ferrites can be used in the GHz frequency range by decreasing the powder particle size and electrically insulating the powders by coating their surface properly.

Simulation and experimental study of the particle size distribution and pore effect on the crystallization of glass powders

Surface nucleation is a frequent phenomenon and plays an essential role in the crystallization of most glasses, especially glass powders used in sintered glass-ceramics, for example. A technique often employed to study the crystallization kinetics of glassy powders is Differential Scanning Calorimetry (DSC). However, the shape of the crystallization peak profile is usually very complex. For instance, in certain cases of surface nucleation, the crystal growth dimensionality may change during crystallization after crystal impingement, and a large density difference between the parent glass and the resulting crystalline phases may produce cavitation pores in the particle volume. Finally, crushed glass particles are not regularly shaped, as assumed in most models. Hence, to evaluate the crystallization kinetics of glass powders by DSC experiments, in this work, we modified and tested a particle crystallization model using the DSC crystallization peaks of jagged powders of a non-stoichiometric (0.95CaO·0.73MgO·2SiO2) diopside glass having different granulometries and a large crystal/glass density difference. The Reis-Zanotto model was adapted to include two complex variables: particle size distribution and crystallization-induced porosity. As predicted by the modified model, we confirmed the radical change of the DSC peak shape for some particle sizes as a result of crystal impingement and pore formation. This combined experimental-simulation study demonstrates that the adapted model can describe this type of complex and yet frequent crystallization case.

Nanomaterial-Based Carbon Paste Electrodes for Voltammetric Determination of Naproxen in Presence of Its Degradation Products.

The present work describes a novel, simple, and fast electroanalytical methodology for naproxen (NAP) determination in pharmaceutical formulations and biological fluids in the presence of its degradation products. Carbon paste electrodes (CPEs) modified with different carbon nanomaterials, namely, glassy carbon powder (GCE), multiwall carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), graphene nanosheets (Gr), and graphene oxides (GO) were tested. Comprehensive studies were performed on the electrode matrix composition including the nature of the pasting liquids, pH, carbon nanomaterials, and mode of electrode modification. Two anodic oxidation peaks were recorded at 0.890 and 1.18 V in 1 × 10−1 mol·L−1 phosphate buffer solution at pH 6. Oxidation of naproxen (NAP) is an irreversible diffusion-controlled process. Calibration plots were rectilinear in the concentration ranging from 0.067 to 1.0 µg·mL−1 with correlation coefficient 0.9979. Photodegradation of NAP resulted in disappearance of the oxidation peak at 1.18 V, allowing simultaneous determination of NAP in presence of its degradation product. The achieved high sensitivity and selectivity suggest the application of the proposed protocol for naproxen determination in pharmaceutical preparations and human blood plasma.

Microstructure and Mechanical Properties of Zr–Al–Ni–Cu Metallic Glassy Particles Reinforced 7056 Al Alloy Matrix Composites Obtained by Spark Plasma Sintering

New 7056 aluminum alloy matrix composites reinforced with Zr55Al10Ni5Cu30 metallic glassy particles are successfully fabricated by spark plasma sintering (SPS) combined with gas‐atomization method. The highly dense bulk body is obtained by utilizing the viscous flow behavior of the glassy powder within the supercooled liquid region. The addition of amorphous reinforcing phase significantly increases the yield strength of Al alloys in compression from 322 to 455 MPa, with retaining a fracture strain ranging between 26% and 16%. It is confirmed that the mutual diffusion of elements takes place between Al alloy matrix and glassy reinforcement during SPS process. The imposed stress and temperature by SPS affect the mutual diffusion and elemental distribution at interface. The increased mechanical response is ascribed to the uniform distribution of the glassy particles and good interfacial bonding. The mechanical properties of such composites can be accurately described by the iso‐stress model involving the matrix‐strengthening mechanism.

Remarkable Oxygen‐Evolution Activity of a Perovskite Oxide from the Ca2−xSrxFe2O6−δ Series

AbstractHerein in we report the unprecedented catalytic activity of an iron‐based oxygen‐deficient perovskite for the oxygen‐evolution reaction (OER). The systematic trends in OER activity as a function of composition, defect‐order, and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca2Fe2O6−δ&lt;CaSrFe2O6−δ&lt;Sr2Fe2O6−δ. Sr2Fe2O6−δ also has the highest electrical conductivity and a unique type of defect‐order. In conventional experiments using glassy carbon electrode, Sr2Fe2O6−δ shows better OER activity than the current state of the art catalysts, Ba0.5Sr0.5Co0.8Fe0.2O3−δ and RuO2. It also offers a high intrinsic electrical conductivity, which allows it to act as a catalyst without the need for glassy carbon electrode or carbon powder. Pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.

Remarkable Oxygen-Evolution Activity of a Perovskite Oxide from the Ca2-x Srx Fe2 O6-δ Series.

Herein in we report the unprecedented catalytic activity of an iron-based oxygen-deficient perovskite for the oxygen-evolution reaction (OER). The systematic trends in OER activity as a function of composition, defect-order, and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca2 Fe2 O6-δ <CaSrFe2 O6-δ <Sr2 Fe2 O6-δ . Sr2 Fe2 O6-δ also has the highest electrical conductivity and a unique type of defect-order. In conventional experiments using glassy carbon electrode, Sr2 Fe2 O6-δ shows better OER activity than the current state of the art catalysts, Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ and RuO2 . It also offers a high intrinsic electrical conductivity, which allows it to act as a catalyst without the need for glassy carbon electrode or carbon powder. Pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.

Metallic glassy Ti2Ni grain-growth inhibitor powder for enhancing the hydrogenation/dehydrogenation kinetics of MgH2.

Because of its high thermal stability and poor hydrogenation/dehydrogenation kinetics, magnesium hydride (MgH2) requires mechanical treatment and/or doping with catalytic agents(s) to understand the decomposition temperature and accelerate the gas uptake/release kinetics. Whereas all catalytic species used for this purpose are crystalline materials, in this paper use of titanium nickel (Ti2Ni) metallic glassy (MG) nanopowders for enhancing the hydrogenation/dehydrogenation kinetics behavior of MgH2 powders is reported. In the present research, MG-Ti2Ni ribbons, prepared using a melt spinning technique were snipped into small pieces and then cryo-milled under a flow of liquid nitrogen to obtain submicron-powders (500 nm). The as-prepared MgH2 powders were doped with 10 wt% of the glassy powder and then cryo-milled for 25 h. The structural and morphological analysis indicated that the cryo-milling process succeeded in maintaining the short-range order structure of MG-Ti2Ni, and in reducing the MgH2 grain size to the nanolevel. The results showed that the as-prepared nanocomposite powders obtained after 25 h of cryo-milling decomposed at 283 °C, with an apparent activation energy of 87.3 kJ mol−1. The MgH2/10 wt% MG-Ti2Ni nanocomposite powders were cold rolled into thin strips, using a cold rolling technique. These cold rolled strips possessed excellent morphological characteristics, shown by the homogeneous distribution of the MgH2 spherical particles (10 nm in diameter) in the glassy Ti2Ni matrix. Furthermore, the hydrogenation/dehydrogenation kinetics measured at 225 °C were very fast, as indicated by the short time (400 s) required to uptake/release 5.7 wt% H2. At this temperature, the system possessed good life-time cycling performance – achieving 84 continuous cycles within 30 h without failure or degradation.

Porous Ti-based bulk metallic glass with excellent mechanical properties and good biocompatibility

Porous Ni- and Be-free Ti-based (Ti45Zr10Cu31Pd10Sn4) bulk metallic glass (BMG) with a diameter exceeding 15 mm was developed by spark plasma sintering (SPS) the mixture of gas-atomized Ti-based glassy alloy powder and solid salt (NaCl) powder, followed by leaching treatment to eliminate the salt phase. The thermal and structural stability, microstructure, mechanical properties, corrosion behavior, and biocompatibility of the developed porous Ti-based BMG samples were investigated systematically. The developed porous Ti-based BMG alloy exhibited three times higher yield strength than that of the natural bone, simultaneously matched the Young's modulus of natural bone, and demonstrated high corrosion resistance and excellent biocompatibility. These results suggest that porous Ti-based BMGs produced by the SPS process open an advanced alternative for clinical applications under load-bearing conditions such as surgical implants.

Ball-Milling of Gas Atomized Al&lt;sub&gt;88&lt;/sub&gt;Ce&lt;sub&gt;8&lt;/sub&gt;Fe&lt;sub&gt;4&lt;/sub&gt; Powders

Gas atomized Al88Ce8Fe4 alloy powders were ball-milled and investigated at charge ratiosof 5:1, 15:1 and 30:1 and milling speeds of 150 and 200 [RPM], respectively. The morphology,microstructure and composition of the powders were examined by laser diffraction technique, SEM,EDS and XRD. The result indicates the evolution of the powders under milling experiences initiallycold welding, aggregating the powders into larger-sized disk-shaped particles; followed byfragmentation, forming smaller-sized equiaxed particles; and finally leading to a steady state, whereparticles morphology, composition and phases keep constantly unchanged. This procedure has beentestified as a general rule for milling at each of the charge ratios of 5:1, 15:1 and 30:1 and at millingspeeds of 150 and 200 [RPM] while milling at larger charge ratios or higher speeds drives faster toreach the steady state at which homogeneous, fine-sized glassy powders can be obtained.