Amorphous Powder Research Articles

Adding high entropy alloys to improve microstructure and properties of laser cladding Fe-based amorphous coatings

In this study, the A-H coatings (abbreviation for Fe-based amorphous and high-entropy alloy), which is consist of Fe-based amorphous powders and adding trace high-entropy alloy (HEA) powders, were prepared via laser cladding technique. The microstructure and properties of the A-H coatings and the Fe-based amorphous coatings were investigated in detail using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). It is found that the number of pores, cracks and dendrites of the A-H coatings is reduced due to the formation of Fe3Ni embedded in amorphous phase compared with Fe-based amorphous coatings. The average microhardness of the A-H coatings is about 1519.2±35.7 HV0.2, which is improved by 38.7%. The wear rate of the A-H coatings is found to decrease by 45.8%. Furthermore, A-H coatings exhibited exceptional corrosion resistance, with a polarization resistance that increased by 31.7%. The addition of HEA is a potential strategy to improve microstructure and properties of Fe-based amorphous coatings.

Enhanced Mechanical Properties of Al2O3 Nanoceramics via Low Temperature Spark Plasma Sintering of Amorphous Powders.

In this work, Al2O3 nanoceramics were prepared by spark plasma sintering of amorphous powders and polycrystalline powders with similar particle sizes. Effective comparisons of sintering processes and ultimate products depending on starting powder conditions were explored. To ensure near-full density higher than 98% of the Al2O3 nanoceramics, the threshold temperature in SPS is 1450 °C for polycrystalline Al2O3 powders and 1300 °C for amorphous powders. The low SPS temperature for amorphous powders is attributed to the metastable state with high free energy of amorphous powders. The Al2O3 nanoceramics prepared by amorphous powders display a mean grain size of 170 nm, and superior mechanical properties, including high bending strength of 870 MPa, Vickers hardness of 20.5 GPa and fracture toughness of 4.3 MPa∙m1/2. Furthermore, the Al2O3 nanoceramics prepared by amorphous powders showed a larger dynamic strength and dynamic strain. The toughening mechanism with predominant transgranular fracture is explained based on the separation of quasi-boundaries.

Design of bimorphic-bimodal microstructure in titanium alloys by semi-solid sintering

We have innovatively achieved bimorphic-bimodal microstructures (BBMs) by semi-solid sintering of TiNbNiCu(Al/Sn) amorphous alloy powders. The BBM contains equiaxed ultrafine-grain matrix, which inherits crystallized equiaxed microstructure after solid sintering, of fcc MTi2 (M = Cu, Ni) embeded into bcc β-Ti, accompanied by isolated regions with coarse β-Ti surrounded by ultrafine-grain fcc MTi2 shell, which originate from fast growth of crystallized β-Ti formed during solid sintering and rapid cooling of fcc MTi2 melt during semi-solid sintering. Resultantly, the BBMs exhibit high an ultimate compressive strength of 2567 MPa and a large plastic strain of 38.1%, superior to those of similar titanium alloys fabricated by melt solidification. The excellent mechanical properties are attributed to the multiplication of slip bands, which are formed in bcc β-Ti phase regions and intercepted by fcc MTi2 phases in the BBM titanium alloys. We anticipate that our work could provide a new strategy for designing lightweight and high-performance materials.

Microstructure, corrosion resistance, and antibacterial property of HVAF-sprayed Cu55Ti25Zr15Ni5 coating

The aim of this paper is to develop a protective coating with both corrosion resistance and microbially-influenced corrosion resistance. We reported a Cu55Ti25Zr15Ni5 amorphous powder, which was deposited into a coating by high velocity air-fuel spray. The coating was characterized via X-ray diffractometer, field-emission scanning electron microscope, and transmission electron microscope. For the electrochemical behavior, potentiodynamic polarization and electrochemical impedance spectroscopy were employed. Antibacterial property was assessed in terms of the inhibitory effect on Pseudomonas aeruginosa. The study findings revealed a crystallization temperature of 465 ℃ for the powder. The coating was dense with a lamellar structure, consisting of amorphous phase, Cu0.81Ni0.19 and tetragonal-ZrO2. In seawater, the coating showed a polarization resistance of 8581 Ω·cm−2, with corrosion dominated by Warburg diffusion. The coating formed a natural Cu2O-ZrO2-TiO2 film, while the corrosion products consisting of CuO, ZrO2, and TiO2. Notably, the coating displayed a bactericidal rate of (83.1 ± 4.5)% within 24 h. This work provided valuable insights into the preparation of Cu-based amorphous coating, while demonstrating its potential to resist microbially-influenced corrosion.

Dispersion of hydrophobic waste amorphous carbon powder in cementitious environment and its effect on the permeability of cement paste

A Proper dispersion of powder-based hydrophobic admixtures in cementitious composites is challenging due to the presence of water. Studies have shown that amorphous carbon powder (ACP), a hydrophobic by-product of refining waste materials of paraffin production can be used as a hydrophobic agent. However, mixing methods and dispersing agents for modifying cementitious materials with ACP can significantly impact their mechanical properties, workability, water-repellency (hence the durability), and dispersion quality of ACP. Lack of information about the extent of their impact on different aspects mentioned above can hinder the practical use of ACP as a hydrophobic agent. To fill this gap, the objective of this study is to comprehensively investigate factors in the dispersion of ACP in cementitious materials and the tradeoff between mechanical properties and water permeability of ACP-modified cementitious materials when more than one mixing method is adopted. The impacts of different dispersing agents and mixing methods, including ultrasonication, dry mixing, and after mixing, on dispersion quality of ACP in cementitious environment analogous with aqueous solutions and hardened cement paste were assessed. Polycarboxylate ether-based superplasticizer (PCE) proved to be the most effective dispersing agent. Compressive strength of ACP modified cement paste can be increased or decreased with or without the workability reduction effect of ACP along with PCE respectively. Based on volume fraction of ACP clusters in X-ray micro-CT 3D reconstruction of hardened cement paste, ultrasonication was identified as the most effective mixing method and dry mixing was the worst in terms of achieving a uniform distribution of ACP in cement paste. However, all mixing methods presented more than 85% volume fraction of uniformly dispersed ACP areas with no major difference in terms of hydrophobic modification capability. Modifying cement paste with a higher amounts of ACP (5 to 15% by weight of cement) substantially increased water contact angle (up to 171% for w/c ratio of 0.35) and decreased water absorption. The hydrophobic modification capability of ACP increases with a decrease in the quality of cement paste and is diminished by the presence of PCE. Consequently, without PCE, water absorption rate was reduced by up to 92% in similar ACP modified cement paste samples, which also led to a major reduction in compressive strength.

Emulsion synthesis and transformations of electrokinetic potential of amorphous and crystal TiO2 particles in water, chloroform, n-decane, and n-decane–chloroform mixture

Sols of TiO2 nanoparticles are promising both as the liquid-phase materials in the electrophoretic display (e-book) technology and as the precursors for the formation of various surface films and bulk porous composites with advanced optical, catalytic, photovoltaic and sorption properties. In this work, the synthesis of ultradispersed amorphous TiO2 powders in reverse emulsions stabilized by АОТ is proposed. Sols were obtained from the powders by ultrasonic dispergation in water, n-decane and n-decane–chloroform mixtures. In distinction to commercial nanoparticles, the synthesized amorphous particles in n-decane exhibited a high negative (–55 ± 7 mV) ζ-potential, while in chloroform – a positive (32 ± 3 mV) one. Thermolysis (300–900 °С) of amorphous powders led to the formation of known individual and mixed polymorphous modifications. Surface recharging of amorphous particles was achieved by different methods: by varying the pH of the hydrosol, by dilution of n-decane organosols with chloroform, addition of АОТ, and variation of thermolysis temperature. A wide spectrum of surface charge states and sizes of TiO2 particles in hydro- and organosols was obtained, which makes the produced systems promising for the sorption of both the water-soluble and solvent dyes of different types.

Pulse ultrasonication leaching approach for selective Li leaching from spent LFP cathode material

ABSTRACT Lithium-iron-phosphate (LFP) batteries are a type of battery whose usage is increasingly expanding due to their features and low production costs. The recovery of precious metals from discarded LFP batteries, resulting from their growing utilization, holds significance from both environmental and economic perspectives. Hydrometallurgical recycling of LFP has gained attention due to its cost-effectiveness and environmental considerations. This study explores the application of ultrasound-assisted leaching as an alternative to conventional hydrometallurgical leaching processes, yielding promising results. The utilization of ultrasound facilitates efficient Li solubility within a short duration of 15 min, eliminating the need for prolonged leaching times. Moreover, selective Li solubility was achieved without the use of additional oxidizing agents through the calcination of the LFP cathode powders. In the ultrasonic leaching of uncalcined powders, a Li dissolution efficiency of 98.60% was obtained, while the Fe dissolution efficiency remained at 32.46%. However, in the ultrasonic leaching of calcined powders, the Li dissolution efficiency was 90.66% within 15 min, while the Fe leaching efficiency remained at 4.88%. Thermodynamic models were employed to elucidate all leaching processes, and the influential parameters were discussed. Furthermore, Al current collectors were successfully recycled, resulting in the production of amorphous Al2O3 powders.

Effects of Ti–V pair substitution and grain boundary modification on physical and magnetic properties of Sm(Fe0.8Co0.2)12 bulk magnet

We successfully fabricated high-density Sm(Fe0.8Co0.2)12–2xTixVx (0.6 ≤ x ≤ 1.0) bulk magnets with high-purity ThMn12-type phase through the bulking of amorphous powder and subsequent annealing process. Depending on the Ti–V pair concentrations, the physical and magnetic properties including lattice constants, crystallized phases, magnetizations (M), and coercivities (Hc) of the fabricated samples were investigated. The highest maximum energy product, (BH)max, of 7.293 MGOe was obtained with x = 0.6; however, its Hc was limited to 3379 Oe due to the absence of a grain boundary phase, despite the average grain size being within 81 nm, which is close to the single domain size. Thus, an intergranular phase was developed by introducing Cu–Ga additive, i.e., Sm(Fe0.8Co0.2)10.8Ti0.6V0.6 + y wt. % Cu–Ga (1 ≤ y ≤ 3), to enhance the Hc. Uniform grain boundaries with Sm-rich phases were crystallized for y ≥ 2, and their thicknesses increased with higher y; the thickness of the grain boundary for the sample with y = 2 was 12 nm. The Hc of the samples with uniform grain boundaries were significantly enhanced from 3379 Oe to 4054 and 4317 Oe for y = 0 and y = 2 and 3, respectively. This paper presents the results of Ti–V pair substitution and grain boundary modification in an effort to improve magnetic properties by controlling crystalline phases, grain sizes, and grain boundaries.

Enhanced microwave absorption performance of FeSiBCCr flake amorphous powder from ball milling

Enhanced microwave absorption performance of FeSiBCCr flake amorphous powder from ball milling

MICROSTRUCTURE AND HIGH-TEMPERATURE WEAR BEHAVIOR OF FE-BASED AMORPHOUS COATINGS BY LASER CLADDING

FeCrMoCB amorphous coatings were prepared on 316 stainless steel via an amorphous powder. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were used to analyze the microstructure, composition, and phase structure of the coatings. Hardness and friction wear testers were applied to investigate the microhardness and wear behavior of the coatings. Results show that the Cr23C6, Cr15Fe7C6 and Fe3Mo crystal phases appeared after laser cladding relative to the complete amorphous powder, and the amorphous phase fraction of the coating was calculated up to 68.4 % using the Verdon method. The coating exhibited a dominating adhesive wear mechanism under room temperature (RT) and transformed to a fatigue wear mechanism as wear test temperature increased to 600 °C. As the temperature was elevated from RT to 600 °C, the wear rate increased from 26 × 10–6 mm3/N·m to 79 × 10–6 mm3/N·m. The laser-cladded Fe-based amorphous coating exhibited much stronger wear performance than the 316 stainless steel, even the wear rate reached one third of that of steel.

Formation mechanism of Fe-based amorphous powders produced by spark erosion

Spark erosion is a convenient, flexible, and low-cost method to quickly produce fine powders of metals, alloys, and semiconductors in size ranging from nearly a hundred micrometers to submicrometer by repetitive spark discharges. Due to the complexity of the powder-forming journey, normally accompanied by high temperature, high pressure, decomposition, diffusion and rapid quenching caused by discharge plasma, the mechanisms of powder formation and possible contaminant infiltration are still controversial, posing a significant challenge to control particle size and chemical composition of the powder produced by this method. In this study, Fe-based amorphous powders in different particle-size distributions with high sphericity were fabricated by spark erosion under different discharge-energy conditions. The maximum particle size of the resultant powders can be correlated with discharge parameters, crater depth, and crater radius, respectively. A multi-ring-breakup model is proposed to reveal the particle-size distribution of the powder formed from the electrode melt under a single-pulse discharge. Furthermore, a dielectric-element infiltration model is provided to quantitatively evaluate the infiltration mass ratio of the contaminant elements, stemming from the decomposed products of dielectric liquid, in the resultant powder with different particle sizes. The models verified through the experimental data are significant for the development of high-performance fine Fe-based amorphous powder with controlled particle size and chemical composition.

Inhomogeneity of the Backward Extruded NdFeB Ring Magnet Prepared from Amorphous Powders.

Back extrusion is an important process to prepare radially oriented NdFeB ring magnets. In this work, we fabricate the ring magnets using amorphous magnetic powders as the raw material. The microstructure, magnetic properties, corrosion resistance, and mechanical properties of the backward extruded magnet at different positions along the axial direction have been investigated, and the inhomogeneity of the magnet is clarified. The results showed that the grains in the middle region of the ring magnet exhibit a strong c-axis orientation, whereas the grains at the bottom and top regions are disordered with random orientation. The microstructure variation is related to the distribution of the grain boundary phase and the degree of grain deformation. Due to the microstructure difference, the magnetic properties, temperature stability, corrosion resistance, and mechanical properties in the middle region of the magnet are higher than those in the top and bottom regions. The exchange coupling between grains also varies in different regions, which is related to the grain size and grain boundary thickness. In addition, different Co element segregations were observed in different regions, which has a crucial effect on the Curie temperature and thermal stability of the magnet. The microstructure difference also leads to the variation of corrosion resistance and mechanical properties for the samples from different regions of the magnet. This work suggests that the amorphous powder can be used to directly prepare radially oriented ring magnets, and the inhomogeneity of the magnet should be fully understood.

A scalable slurry process to fabricate CuZr amorphous alloy with hybrid lithiophilic oxides for lithium metal anode

The lithium metal is the most promising candidate anode for the next-generation lithium batteries, its wide-scale application will be accelerated if its electrode preparation process is feasible and compatible with the current electrode preparation approach used in the battery industry. Here the powder form of CuZr metallic glass was applied for lithium metal anode application, which was one-step chemically dealloying treated in the hydrofluoric acid solution prior to usage. The as-prepared CuZr powder (CuZr-D*) displays enlarged specific surface area with hybrid lithiophilic CuxO/ZrO2 oxides decorated on the surface, which is capable to induce homogenous nucleation, promote fast reaction kinetics, and improve the reversible lithium plating/stripping process. Moreover, the CuZr in powder form makes it easily accessible with the slurry-based electrode preparation process currently applied in battery industry. As a result, the CuZr-D* based electrode demonstrates good symmetric cell performance of 1500 h at 1.0 mA cm−2/1.0 mAh cm−2, high coulombic efficiency of 97.5% after 200 cycles at 0.5 mA cm−2/1.0 mAh cm−2, cyclic stability and rate capability of full cells. This work supports the potential feasibility of amorphous alloy powder for lithium metal battery application.

Composition design of high Bs Fe-based amorphous powders with good sphericity

Fe83SixByC(17-x-y) has good glass forming ability (GFA), and high saturation magnetic induction (Bs), and spherical amorphous powder can be prepared using a gas–water coupling atomization (GWC) device. Herein, the effects of metalloid elements (B, C, Si and P) on the thermal parameters and magnetic properties of the Fe83SixByC(17-x-y) powder are discussed. The research conclusion shows that the Fe83Si2.5B11.5C3 amorphous powder exhibits the best comprehensive performance. Through the Lorentz microscope pattern of Fe83Si2.5B11.5C3 amorphous powder, magnetic domains walls are observed to gather and interlace in the outer region of the particle. The Fe83Si2.5B11.5C3 amorphous powder exhibits a high initial crystallization temperature (Tx1), followed by a ΔTx of 27 ℃, and then crystallization completion at 561.1 ℃. Some clusters or primary crystals are produced in the amorphous matrix after annealing at 520 ℃ (below Tx1 534 ℃) for 1 h. A further increase in the annealing temperature to 570 ℃ (beyond Te1 561.1 ℃) causes the precipitation of a large amount of crystalline phase α- Fe (Si) and hard magnetic phase Fe2B, thereby resulting in the rapid deterioration of the magnetic properties of the amorphous powder.

Amorphous/crystalline Zn60Zr40 alloys lattice structures with improved mechanical properties fabricated by mechanical alloying and selective laser melting

ABSTRACT In the present study, mechanical alloying (MA) was employed for synthesising non-equilibrium Zn60Zr40 amorphous powders, and then consolidated into amorphous/crystalline Zn60Zr40 alloys using selective laser melting (SLM). The results showed that the MA process destabilised the atomic periodicity of Zn and Zr powders and induced crystalline-to-amorphous transformation due to atomic size mismatch and negative heat of mixing. Moreover, the amorphisation trend of as-milled powders was intensified with increasing milling time and attained almost fully amorphous structure after 30 h of milling. During SLM, the ultra-high cooling rate restricted the long-range atomic diffusion of the amorphous powders and enabled successful survival of amorphous phase, leading to amorphous/crystalline Zn60Zr40 alloys. The alloys exhibited a maximum compressive yield strength and microhardness of 160.9 ± 9.1 MPa and 3.73 ± 0.8 GPa, respectively. These findings demonstrated that the developed MA-SLM process might be a promising strategy for the preparation of amorphous/crystalline alloys with superior properties.

Ecological and toxicological assessment of hazard of contamination of water bodies by the γ-polyoxymethylene

Introduction. In the process of production, storage and application of the representative of new components of solid rocket fuels – γ-polyoxymethylene, its ingress into the water of reservoirs is not excluded, which determines the mandatory assessment of the danger of its single contamination of this ecosystem.
 Material and methods. As an object of research, γ-polyoxymethylene (γ-POM, polyformaldehyde, acetal copolymer) was used – a mixture of dimethyl esters of polyoxymethylene glycols – a fine amorphous white powder, CAS registration number 66455-31-0. The empirical formula is CH3O(CH2O)nCH3 at n = 100–300. It is practically insoluble in water.
 Results. It was found that the ecotoxicant content in water at a concentration of 50.0 mg/l led to a change in its transparency. The indicated concentration of γ-POM was determined as a threshold for organoleptic harmfulness.
 In the course of studying the effect of the toxicant on the general sanitary regime of reservoirs, in the absence of changes in the indicators of biochemical oxygen consumption, its negative impact on nitrification processes and saprophytic microflora was revealed. The threshold concentration of the substance according to the general sanitary indicator of harmfulness is 3.5 mg/l.
 In experiments on laboratory animals, it was noted that a single intragastric administration of the tested xenobiotic in the form of a suspension in a 2.5% solution of aqueous starch caused a significant decrease in heart rate and a change in a number of hematological parameters. The threshold of a single general toxic effect of γ-POM is 90.0 mg/kg.
 Limitations of the study. The revealed features of the behavior of γ-polyoxymethylene must be taken into account when it once pollutes the water of reservoirs (in case of an emergency). However, the data obtained are insufficient to substantiate the hygienic standard of the connection in the water of water bodies.
 Conclusion. The results of the performed experiments indicate that a single ingress of γ-polyoxymethylene into the water represents an ecological and toxicological hazard registered for all three basic signs of harmfulness, which is taken into account when justifying its maximum permissible concentration in the water of reservoirs.

Selective/simultaneous batch adsorption of binary textile dyes using amorphous perlite powder: aspects of central composite design optimization and mechanisms.

The online version contains supplementary material available at 10.1007/s40201-023-00870-1.

Magnetic properties of phosphoric acid passivated Fe-Si-B amorphous magnetic powder core

The magnetic properties of Fe-Si-B amorphous soft magnetic powder cores (SMCs) passivated by phosphoricacid are investigated in this work. Effects of phosphoric acid content and annealing temperature at different frequencies on permeability and magnetic loss of SMCs have been studied, too. Electronic microscope pictures and results of B-H analyzer show that the surface of Fe-Si-B SMCs is coated with a layer of dense phosphate. Experimental results show that Fe-Si-B SMCs with the best comprehensive magnetic properties (μe = 23.71; Pcv = 470.6 mW•cm−3 measured at 1000 kHz, 20 mT) can be obtained by adding 0.8 wt% phosphoric acid at the annealing temperature of 480 °C.

Boron-containing plastic composites as neutron shielding material for additive manufacturing processes

A study of samples of shielding materials which exploit plastic as the basis of neutron absorbing composite with 25%–37% weight boron-containing powder has been provided. Composite samples were prepared by fused filament fabrication (FFF). Acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG) plastics were used as the polymer matrix material, while boron nitride powder and amorphous boron powder were used as boron-containing fillers.According to measurements of the neutron transmission on the monochromatic beam of the IR-8 reactor (main monochromatic neutron beam line - 2.4 Å), the use of boron as a filler in the plastic provides a decrease in the penetration depth of neutrons by 56%–78%: from 3.0 mm for a sample of plastic without filler to 0.65 mm for a sample with amorphous boron powder.Tensile and bending mechanical tests showed that the addition of boron-containing powder leads to development of brittleness of composite materials. The boron-containing samples experienced a 40%–55% of strength decrease and the failure of samples occurred without plastic deformation, while in ABS and PETG samples the plastic deformation takes up a significant portion of the test diagram.

Bond strength characteristics of high strength alkali activated slag concrete mixes

Bond characteristics are influenced by several factors such as concrete compressive strength, type, diameter, and embedment length of the bar and confinement of concrete. Herein, an attempt has been made to evaluate the bond strength characteristics of a new class of high-strength, flowable, alkali activated slag concrete mixes made using the industrial by-products from iron and steel industries. Such evaluations are made using the results of direct pull out tests where again, the bond stress – slip behaviour of the trial mixes at different ages are also studied. GGBFS was used as the principal binder along with fine amorphous quartz powder in the development of the present class of high strength, flowable AASC mixes. While mixtures of steel slag sand and quartz sand were used as the fine aggregates, 12.5 mm down electric-arc furnace slag aggregates constituted the coarse aggregate fractions in all these mixes. The alkaline solutions used consisted of mixtures of specified amounts of sodium hydroxide flakes dissolved in the calculated quantity of water pre-mixed with the liquid sodium silicate solution. The experimental study was planned based on Taguchi’s design of experiments methodology. A set of AASC mixes were developed and evaluated for their workability characteristics along with compressive strengths at the ages of 3, 28, 56 and 90 days. Bond strength characteristics of a set of nine of such mixes were evaluated in an initial calibration phase. Strength prediction equations were then derived based on those initial results, the predictive capability of which were then assessed and ascertained with actual results of experiments on a set of six new mixes, in the prediction phase. Further better bond stress-slip behavior, with higher bond strength values, varying in the range of 12–14 MPa as compared to control OPC based reference concrete mix were obtained for the AASC mixes.