High-energy Milling Research Articles

Scalable Synthesis and Electrochemical Properties of Porous Si-CoSi2-C Composites as an Anode for Li-ion Batteries.

Si-based anodes for Li-ion batteries (LIBs) are considered to be an attractive alternative to graphite due to their higher capacity, but they have low electrical conductivity and degrade mechanically during cycling. In the current study, we report on a mass-producible porous Si-CoSi2-C composite as a high-capacity anode material for LIBs. The composite was synthesized with two-step milling followed by a simple chemical etching process. The material conversion and porous structure were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy. The electrochemical test results demonstrated that the Si-CoSi2-C composite electrode exhibits greatly improved cycle and rate performance compared with conventional Si-C composite electrodes. These results can be ascribed to the role of CoSi2 and inside pores. The CoSi2 synthesized in situ during high-energy mechanical milling can be well attached to the Si; its conductive phase can increase electrical connection with the carbon matrix and the Cu current collectors; and it can accommodate Si volume changes during cycling. The proposed synthesis strategy can provide a facile and cost-effective method to produce Si-based materials for commercial LIB anodes.

Use of XRD technique to investigate the stability of quasicrystalline phase in high-energy milled Al/AlCuFe powders

Quasicrystalline alloys have excellent potential for being used in composites. They have high hardness, low friction coefficient and, in particular for AlCuFe, the components have high availability. The quasicrystal of the AlCuFe alloy can especially work well as reinforcements in aluminium matrix composites, contributing to increasing hardness, when compared to pure aluminium. Depending on the method used to obtain the composite, high-energy milling is necessary to mix the powders of the matrix and the reinforcement. Therefore, this work aimed to investigate the stability of quasicrystalline phase in Al/AlCuFe powders milled using XRD technique. For this, Al/AlCuFe powders were milled in high energy planetary ball mill in proportions of 10 and 20%vol. of AlCuFe. XRD analysis were then carried in the samples. The results showed that, for the parameters used, there was no phase transformation during milling.

Characterization of MCrAlY/nano-Al2O3 nanocomposite powder produced by high-energy mechanical milling as feedstock for high-velocity oxygen fuel spraying deposition

Characterization of MCrAlY/nano-Al2O3 nanocomposite powder produced by high-energy mechanical milling as feedstock for high-velocity oxygen fuel spraying deposition

High-Performance Core-Shell Structured SiOx@Si-Silicide Nanocomposite Anode Material for Lithium-Ion Rechargeable Batteries

Si-based materials are the most promising anode candidates for high-performance and safe lithium-ion batteries (LIBs). However, their successful practical utilization is hampered due to the large volume variations during the alloying/dealloying process, structural instability, and poor conductivity. To address these issues, herein, we report a novel double-protection strategy for Si with a mechanically strengthen and conductive FeSi2 phase and SiOx core–shell structure (SiOx@Si-FeSi2 nanocomposite) synthesized via induction melting followed by high-energy mechanical milling and thermal oxidation. A high initial cycle coulombic efficiency (∼79%) and high reversible capacity of ∼843 mAh/g@220th cycle (under 1C-rate = 0.5 A g−1) is achieved for the SiOx@Si-FeSi2 nanocomposite. Moreover, high average coulombic efficiency of ∼99.1% and high reversible capacity retention of ∼80% (at 1C-rate) over 200 cycles; and excellent rate capability is obtained. The outstanding electrochemical performance of the SiOx@Si-FeSi2 nanocomposite is attributed to the synergistic effect of well dispersed active Si in the FeSi2 phase. Additionally, an amorphous SiOx core–shell structure significantly reduces the mechanical stresses/strains experienced by Si during lithiation/delithiation. It also provides a stable solid electrolyte interface and good conductivity. Subsequently, this facile, cost-effective synthetic approach providing excellent electrochemical performance makes the SiOx@Si-FeSi2 nanocomposite a promising anode material for high-performance LIBs.

Selective laser melted CrMnFeCoNi + 3 wt% Y2O3 high-entropy alloy matrix nanocomposite: Fabrication, microstructure and nanoindentation properties

A Y2O3-reinforced equiatomic CrMnFeCoNi high-entropy alloy (HEA) matrix nanocomposite was fabricated by high-energy attrition milling and selective laser melting (SLM) additive manufacturing. The SLM-built HEA nanocomposite possessed heterogeneous grain structures and substructures decorated with a dislocation network and exhibited a high number density of nano-sized Y2O3. The SLM-built HEA + Y2O3 nanocomposite exhibited higher nanohardness (~9.22 GPa) than other equiatomic CrMnFeCoNi HEAs produced by casting (~4.13 GPa) and SLM (~6.95 GPa). This suggested that the dispersion hardening by the Y2O3 nanoparticles enabled superior mechanical properties. This study, therefore, demonstrated that Y2O3 reinforcement can effectively improve the mechanical properties of SLM-built CrMnFeCoNi HEA matrix nanocomposites.

An Engineering Zirconia Ceramic Made of Baddeleyite.

Wet high-energy milling and uniaxial pressing are used to fabricate CaO-stabilized tetragonal zirconia polycrystalline ceramic (Ca-TZP) with decent mechanical characteristics, i.e., a hardness of 11.5 GPa, Young’s modulus of 230 GPa, and fracture toughness of 13 MPa·m0.5. The effect of CaO concentration and the sintering temperature on phase composition and mechanical characteristics of CaO-stabilized zirconia ceramic made of baddeleyite is investigated.

Investigation of characteristics and properties of spark plasma sintered ultrafine WC-6.4Fe3.6Ni alloy as potential alternative WC-Co hard metals

The present study proposed the fabrication of a WC-6.4Fe-3.6Ni hard metal alloy using spark plasma sintering (SPS) as a potential alternative to the WC-Co hard metal. Fe-36%Ni powder (mean particle size 26.9 μm) was produced from Fe and Ni commercial powders via high energy milling and the effect was analyzed. WC-6.4Fe-3.6Ni (alternative grade) and WC-Co (reference grade) were obtained from ultrafine WC powder (particle size 0.45) with 10%wt binder. SPS sintering of WC-6.4Fe3.6Ni was performed at 1100, 1200 and 1300 °C with a holding time of 5 min achieving 99.8% higher densification at 1300 °C and WC-Co was sintered at 1200 °C. The results show that increasing the sintering temperature enhanced the microstructure and hardness with a decrease in fracture toughness. The wettability of milled Fe-Ni binder during heating in the SPS process contributes to enhance densification and properties. The decrease in fracture toughness is attributed to a decrease in the binder mean free path. The XRD analysis showed that η phase was not detected for either composite grades. Studies of sintering kinetics were applied to determine the sintering mechanisms involved in the final stage of sintering, which can be elucidated by calculating the slope exponent (n) from the relationship between the shrinkage rate and sintering time. Slope exponent consistent with WC diffusion in the liquid phase was found for WC-6.4Fe-3.6Ni sintered at 1300 °C. Good properties was found for WC-6.4Fe-3.6Ni sintered at 1300 °C, showing higher hardness ~1633 HV30 and fracture toughness ~11 MPa m0.5. WC-6.4Fe-3.6Ni sintered at 1200 °C has superior hardness (1786 HV30) than WC-Co (1689 HV30). A comparison of these properties with results from similar grades in the literature shows that the WC-6.4Fe-3.6Ni alternative grade has optimal properties and can be adopted as an alternative to WC-Co grades.

High-Energy Mechanical Milling-Driven Reamorphization in Glassy Arsenic Monoselenide: On the Path of Tailoring Special Molecular-Network Glasses.

The impact of high-energy milling on glassy arsenic monoselenide g-AsSe is studied with X-ray diffraction applied to diffuse peak-halos proper to intermediate- and extended-range ordering revealed in first and second sharp diffraction peaks (FSDP and SSDP). A straightforward interpretation of this effect is developed within the modified microcrystalline approach, treating “amorphous” halos as a superposition of the broadened Bragg diffraction reflexes from remnants of some inter-planar correlations, supplemented by the Ehrenfest diffraction reflexes from most prominent inter-molecular and inter-atomic correlations belonging to these quasi-crystalline remnants. Under nanomilling, the cage-like As4Se4 molecules are merely destroyed in g-AsSe, facilitating a more polymerized chain-like network. The effect of nanomilling-driven molecular-to-network reamorphization results in a fragmentation impact on the correlation length of FSDP-responsible entities (due to an increase in the FSDP width and position). A breakdown in intermediate-range ordering is accompanied by changes in extended-range ordering due to the high-angular shift and broadening of the SSDP. A breakdown in the intermediate-range order is revealed in the destruction of most distant inter-atomic correlations, which belong to remnants of some quasi-crystalline planes, whereas the longer correlations dominate in the extended-range order. The microstructure scenarios of milling-driven reamorphization originated from the As4Se4 molecule, and its network derivatives are identified with an ab initio quantum-chemical cluster modeling code (CINCA).

Effect of high-energy attrition milling and La2O3 content on the microstructure of Mo-La2O3 composite powders

Mo-La2O3 composites are potential high-temperature materials for future technology devices operating at temperatures above 1300 °C because of their excellent thermal stability, high mechanical properties and good creep resistance. In this study, we focused on the preparation of Mo-matrix/lanthanum oxide (La2O3) composite powders using high-energy attrition milling. The effects of rotational milling speed (350 and 800 rpm) and La2O3 content (2.5 and 10 vol. %) on the microstructural evolution, phase composition, morphology, and distribution of the second phase in the produced composite Mo-La2O3 powders were investigated in details. The results show that the most interesting composite powder was Mo-10 vol.% La2O3 produced using a rotational speed of 800 rpm, which exhibited better distribution, smaller particle size and higher amount of ceramic phase introduced in the interiors of the Mo grains.

Effect of Milling Parameters on the Development of a Nanostructured FCC–TiNb15Mn Alloy via High-Energy Ball Milling

In this work, a blend of Ti, Nb, and Mn powders, with a nominal composition of 15 wt.% of Mn, and balanced Ti and Nb wt.%, was selected to be mechanically alloyed by the following two alternative high-energy milling devices: a vibratory 8000D mixer/mill® and a PM400 Retsch® planetary ball mill. Two ball-to-powder ratio (BPR) conditions (10:1 and 20:1) were applied, to study the evolution of the synthesized phases under each of the two mechanical alloying conditions. The main findings observed include the following: (1) the sequence conversion evolved from raw elements to a transitory bcc-TiNbMn alloy, and subsequently to an fcc-TiNb15Mn alloy, independent of the milling conditions; (2) the total full conversion to the fcc-TiNb15Mn alloy was only reached by the planetary mill at a minimum of 12 h of milling time, for either of the BPR employed; (3) the planetary mill produced a non-negligible Fe contamination from the milling media, when the highest BPR and milling time were applied; and (4) the final fcc-TiNb15Mn alloy synthesized presents a nanocrystalline nature and a partial degree of amorphization.

Neural network-based model for predicting particle size of AZ61 powder during high-energy mechanical milling

Neural network-based model for predicting particle size of AZ61 powder during high-energy mechanical milling

Synthesis of nanostructured lanthanum hexaboride via simple borothermal routes at low temperatures

Rare-earth hexaborides, especially lanthanum hexaboride (LaB6) are popular materials as thermionic cathodes. It is a great challenge to synthesise these hexaborides at a low temperature without any post-synthesis purification treatments. In this research work, we demonstrate a simple synthesis technique, namely borothermal method for preparing pure lanthanum hexaboride by reacting lanthanum oxide (La2O3) with boron (B). In this investigation, different pressed pellets were made using the starting powders mixed either by milling mildly for 30 min or high-energy milling (HEM) for 8/16 h. Later, the prepared pellets were put into a low-vacuum furnace at different temperatures. The synthesised products were characterised using X-ray diffraction (XRD), scanning electron microscope (SEM), electron dispersive spectroscopy (EDS) and a Schottky device for their structural, chemical, morphological and thermionic properties. Both synthesis methods are found to produce LaB6 with a purity above 99% at a relatively low temperature of 1250 °C. High-energy ball milling does not result in reducing synthesis temperatures, rather introduces some iron impurities. From XRD and SEM investigations, the average crystallite size of pure LaB6 prepared by borothermal methods is observed to be in the range of 225–250 nm. From thermionic emission data, partially sintered LaB6 pellets prepared from powders via the simple borothermal and the borothermal method with HEM exhibit work functions of 2.86 ± 0.05 eV and 2.64 ± 0.08 eV, respectively. The results suggest that nanostructured LaB6 with a low work function can be easily prepared at lower temperatures for applications in thermionic energy converters, high-power electron devices and photonics.

GaP-TiO₂-C Nanocomposite as High-Performance Sodium-Ion Batteries Anode.

GaP-TiO₂-C composites with three different C concentrations are synthesized via a high-energy mechanical milling. The analysis of the structural characteristics of GaP-TiO₂-C using X-ray diffraction and high-resolution transmission electron microscopy reveals that the nanosized GaP and TiO₂ crystallites are uniformly distributed in the amorphous C matrix. The GaP-TiO₂-C(20%) composite exhibits a high Na storage capacity of 266 mAh g-1 at the current density of 0.1 A g-1 after 100 cycles, and the remarkable rate capability of 224 mAh g-1 even at the higher current density of 10 A g-1. In addition, the GaP-TiO₂-C(20%) composite presents great cycling performance and the capacity of 213 mAh g-1 at the current density of 0.5 A g-1 after 300 cycles. The outstanding cycling performance and rate capability of GaP-TiO₂-C(20%) anode can be attributed to the favorable morphology of GaP-TiO₂-C composite that accommodates large volume changes during cycling.

Effect of variations in milling speed with high energy milling treatment on surface area of biochar material

Biochar is a renewable and abundant carbon source and is useful for increasing food security and plant diversity in areas with poor soil conditions, lack of organic matter, lack of water availability and chemical fertilizers. Biochar micro porous structure can be produced from corncob material which inherits the architecture of raw materials. To increase the surface area of the biochar material, high energy milling treatment was carried out in this study by varying the speed of milling in the same milling time. Milling time is carried out at 3 hours with milling speeds varying of 300, 500 and 700 rpm. The samples were characterized by X-ray diffraction, scanning electron microscope (SEM), particle size analyser (PSA), and surface area analysis - Brunauer, Emmett and Teller (SAA-BET). The test results show that at speed of 300, 500 and 700 rpm it has produced biochar with a particle size of 947,9; 868,5 and 799,2 nm, respectively. While the SAA-BET test has produced a surface area of 10.115; 15.889 and 18.303 m2/g. This study describes an increase of surface area when compared without milling treatment which has a surface area of 7917 m2/g.

Ultrafine Cemented Carbides with Cobalt and Iron Binders Prepared via Reactive <i>In Situ</i> Sintering

Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor elemental powders, followed by in-situ synthesis of tungsten carbide. This approach promotes formation of ultrafine microstructure favored in many cemented carbide applications. Our study focuses on the effect of mechanical activation (high-energy milling) on the properties of powder and following thermal activation (sintering) on the microstructure characteristics and phase composition. Reactive sintering proved effective – an ultrafine grained microstructure of cemented carbides with Co and Fe binders was achieved. Formation of tungsten carbide grains was complete at low temperature during reactive spark plasma sintering, resulting in textured microstructure with anisotropic grain formation and growth.

Nanostructured biological hydroxyapatite from Tilapia bone: A pathway to control crystallite size and crystallinity

Hydroxyapatite is the main mineral component of the bone and the main responsible for their hardness and mechanical strength. It shows enormous scientific and technological value as it presents a potential for application in medical purposes and pharmaceutical, chemical, and environmental remedy industries. Many authors have demonstrated the possibility of hydroxyapatite synthesis from different sources and synthesis methodologies. However, studies which lead to an effectively controlled crystallite size and crystallinity are still scarce. Our study aims to evaluate the effects of heat treatment temperature and high energy milling time on obtaining nanometric hydroxyapatite from a natural source. The characterization has been performed by employing thermal, chemical, structural, morphological, and surface area analysis. It has been possible to verify only hydroxyapatite formation. In the milled samples, it's been possible to verify a reduction in the crystallite size and crystallinity. The surface area increased from 0.07 to 41.37 m2/g, but excessive milling times caused agglomeration and reduced the surface area. The results showed that it is possible to synthetize nanostructured hydroxyapatite (9,8–95 nm) with crystallinity ranging from 3 to 99% from Tilapia bones. ANOVA has validated the results. The produced materials present an excellent potential for application in the biomedical or adsorption substances area.

Impact of the SiC addition on the morphological, structural and mechanical properties of Cu-SiC composite powders prepared by high energy milling

The effect of the SiC content on the microstructural, mechanical, and magnetic properties of Cu(1 − x)SiC(x) composite powders (x = 0, 2, 10 and 15 wt%) prepared by high energy milling for 30 h was investigated. The results showed that Cu particles were severely deformed and formed plate like particles of different sizes, while SiC particles were fragmented and embedded in the Cu phase, thus, forming composite particles. As the SiC content increased, the average particle size decreased from 40.75 to 12.84 µm. Besides, XRD data showed a decrease in the crystallite sizes of the Cu phase (from 23.66 to 21.56 nm), accompanied by an increase in the lattice micro-strain (from 0.41 to 0.46%). Changes in the lattice parameters of the Cu phase were observed. The Vickers microhardness were measured in compacted powder samples and reached a maximum value of 135.22 HV for the sample with 15 wt% SiC. The samples showed hysteresis magnetic behavior at 300 K, and with a maximum saturation magnetization of 0.123 emu/g. The weak magnetic signal is mainly due to Co impurities present in the WC from the milling media.

A chemical model to predict the formation of a semiconductor solid solution: New insights in the use of bulk and surface mechanochemical reactions

A chemical model capable of predicting the formation of a semiconductor solid solution, via high-energy milling of powder precursors, is proposed. According to experimental findings provided by X-ray powder diffraction and X-ray photoelectron spectrometry, the model encompasses three major stages related to a series of oxygen levels, which are function of oxygen potential during milling. The initial step involves the formation of oxide mixtures, as evidenced by oxidizing highly reactive chalcogens (Se and Te) and re oxidation of PbO. In the middle step, which represents the largest process stage, Te or Se share electrons to act as Te (IV) and Se (IV) in order to form Pb complex chalcoxides. The formation of high purity Pb2SeTe semiconductor solid solution is detected at the final stage, in such stage the chalcogens act as reducing agents. Consequently, neither inert nor high vacuum atmospheres are required during the milling process. The model involves a quaternary interpretation whose predictions are validated with experimental findings, theoretical, and even analogous phases not reported so far in literature.

Improved fractal kinetic model to predict mechanochemical destruction rate of organic pollutants

Mechanochemical destruction of organic pollutants by high energy milling with inorganic reagents is considered a promising non-thermal technology to detoxify hazardous waste. However, due to complex nature of the physicochemical phenomena involved, pollutant destruction kinetics heavily depends on the used reagents and operating parameters, thus varying case by case. In the present work, a fractal model was validated as flexible tool to interpolate pollutant mechanochemical destruction data satisfactorily. In addition, such model was expanded to estimate the contributions of the inorganic reagent and the pollutant to the overall reaction rate. Specifically, the kinetic constant associated to mechanical activation of the co-milling reagent and that related to pollutant destruction reaction were calculated. Their values resulted to depend only on the specific compound, hence, the tabulated data could be used to predict the pollutant mechanochemical degradation rate for any kind of mixture.

Mechanosynthesis and Thermoelectric Properties of Fe, Zn, and Cd-Doped P-Type Tetrahedrite: Cu12-xMxSb4S13.

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350–400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites’ thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies.