High-energy Ball Milling Treatment Research Articles

Study on electromagnetic wave absorbing properties of nanocrystalline Fe81.5Si3B9P3C1Cu1Ti1.5/Graphene oxide composite

To prevent and control electromagnetic pollution problems, there is an urgent need to develop better wave-absorbing materials. In this study, nanocrystalline alloy/graphene oxide(GO) composite modified powder was obtained on the basis of Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline alloy powder with different weight percentages of GO, which was mechanically mixed by high-energy ball milling treatment, and the microstructure and morphology of the materials and the electromagnetic wave absorption properties were characterized. The results show that the Fe81.5Si3B9P3C1Cu1Ti1.5/GO composite powder has excellent wave absorption performance, and the loss mechanism is magnetic loss including eddy current loss and natural resonance. Defects and groups in GO not only improve the impedance matching characteristics, but also introduce defect polarization relaxation and electron dipole polarization relaxation of the groups, which are beneficial to the penetration and absorption of electromagnetic waves. The minimum reflection loss (RLmin) of the nanocrystalline alloy powder can reach −37.55 dB and the maximum effective absorption bandwidth (ΔfRL<-10dB) can reach 5.95 GHz; the RLmin of the composite powder is as high as −52.55 dB when the GO content is 1.5 wt%, and the widest bandwidth can reach 6.12 GHz at 2.00 mm when the GO content is 0.5 wt%. With the addition of GO, its RLmin increased by 40%. This indicates that the composite material have superior absorption performance compared to a single absorber.

Enhanced Electrochemical Performance of Sugarcane Bagasse-Derived Activated Carbon via a High-Energy Ball Milling Treatment.

Activated carbon (AC) from sugarcane bagasse was prepared using dry chemical activation with KOH. It was then subjected to a high-energy ball milling (HEBM) treatment under various milling speeds (600, 1200 and 1800 rpm) to produce AC nanoparticles from micro-size particles. The AC samples after the HEBM treatment exhibited reduced particle sizes, increased mesopore volume and a rich surface oxygen content, which contribute to higher pseudocapacitance. Notably, different HEBM speeds were used to find a good electrochemical performance. As a result, the AC/BM12 material, subjected to HEBM at 1200 rpm for 30 min, exhibited the highest specific capacitance, 257 F g−1, at a current density 0.5 A g−1. This is about 2.4 times higher than that of the AC sample. Moreover, the excellence capacitance retention of this sample was 93.5% after a 3000-cycle test at a current density of 5 A g−1. Remarkably, a coin cell electrode assembly was fabricated using the AC/BM12 material in a 1 M LiPF6 electrolyte. It exhibited a specific capacitance of 110 F g−1 with a high energy density of 27.9 W h kg−1.

A Low-Cost and Green Si-Based Anode Material for Lithium-Ion Batteries

The conception of cheaper and greener electrode materials is critical for Li-ion battery manufacturers. In this study, it is shown that a by-product of the carbothermic reduction of SiO2 to Si, containing Si, SiC and C materials, can be valorized as a low-cost and high-capacity anode material for Li-ion batteries after an appropriate high-energy ball milling treatment. The latter results in the production of a micrometric powder (D50 ~1 mm) in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix. Such a microstructure prevents the deleterious formation of c-Li15Si4 phase, which is well known to accentuate particle cracking. As a result, the electrode is able to maintain a capacity >1000 mAh g-1 (>3 mAh cm-2) over 100 cycles. Moreover, calendering has no negative impact on the electrode performance. However, a significant and irreversible increase of the electrode mass and thickness was observed over cycling, which is mainly attributed to the accumulation of SEI products. In order to have deeper insights into the microstructural evolution of the electrode during cycling, a focused ion beam (FIB) milled microcavity (45×20×50 µm3) was created in the center of the pristine electrode. This cavity was observed by SEM at different cycling periods of a single electrode (Fig. 1a). This investigation method allows following the same electrode along different steps of its cycling, nearly as for an in-situ method. Additionally, backscattered-electron (BSE) imaging was performed on broad ion beam (BIB) polished cross-section of the electrode after different periods of cycling (Fig. 1b). The morphological change is characterized at the electrode and particle scales by monitoring the thickness, mass, porosity and macrocracking of the electrode, SEI layer thickness and particle morphology. On the basis of these investigations, a more comprehensive view of the degradation phenomena of the electrode is established. Figure 1

Preparation and Electromagnetic Absorption Properties of Fe73.2Si16.2B6.6Nb3Cu1 Nanocrystalline Powder.

In order to decrease and control electromagnetic pollution, absorbing materials with better electromagnetic wave absorption properties should be developed. In this paper, a nanocrystalline alloy ribbon with the composition of Fe73.2Si16.2B6.6Nb3Cu1 was designed and prepared. Nanocrystalline alloy powder was obtained by high-energy ball milling treatment. The effects of ball milling time on the soft magnetic properties, microstructure, morphology, and electromagnetic wave absorption properties of alloy powder were investigated. The results showed that, as time increased, α-(Fe, Si) gradually transformed into the amorphous phase, and the maximum saturation magnetization (Ms) reached 135.25 emu/g. The nanocrystalline alloy powder was flakelike, and the minimum average particle size of the powder reached 6.87 μm. The alloy powder obtained by ball milling for 12 h had the best electromagnetic absorption performance, and the minimum reflection loss RLmin at the frequency of 6.52 GHz reached −46.15 dB (matched thickness was 3.5 mm). As time increased, the best matched frequency moved to the high-frequency direction, and the best matched thickness decreased, while the maximum effective absorption bandwidth ΔfRL<−10 dB was 7.22 GHz (10.78–18 GHz).

Tailoring the structure of MoS2 using ball-milled MoO3 powders: hexagonal, triangular, and fullerene-like shapes

Single and few-layered MoS2 materials have attracted attention due to their outstanding physicochemical properties with potential applications in optoelectronics, catalysis, and energy storage. In the past, these materials have been produced using the chemical vapor deposition (CVD) method using MoO3 films and powders as Mo precursors. In this work, we demonstrate that the size and morphology of few-layered MoS2 nanostructures can be controlled, modifying the Mo precursor mechanically. We synthesized few-layered MoS2 materials using MoO3 powders previously exposed to a high-energy ball milling treatment by the salt-assisted CVD method. The MoO3 powders milled for 30, 120, and 300 min were used to synthesize sample MoS2-30, MoS2-120, and MoS2-300, respectively. We found morphologies mainly of hexagons (MoS2-30), triangles (MoS2-120), and fullerenes (MoS2-300). The MoS2 nanostructures and MoO3 powders were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, x-ray diffraction, and thermogravimetric analysis. It was found that MoO3 milled powders exhibit oxygen loss and decrease in crystallite size as milling time increases. Oxygen deficiency in the Mo precursor prevents the growth of large MoS2 crystals and a large number of milled MoO3-x + NaCl promote greater nucleation sites for the formation of MoS2, achieving a high density of nanoflakes in the 2H and 3R phases, with diameter sizes in the range of ∼30–600 nm with 1–12 layers. Photoluminescence characterization at room temperature revealed a direct bandgap and exciting trends for the different MoS2 samples. We envisage that our work provides a route for modifying the structure and optical properties for future device design via precursor engineering.

Mechanochemically assisted low temperature synthesis route of the 1144 Ca-K Iron Based Superconductor

Among the Iron Based Superconductors, the so-called 1144 family attracts significant interest due to its high critical fields and critical current densities and to the stoichiometric nature of the compounds, disentangling the superconducting properties from the compositional homogeneity. Their practical application is partly hindered by the severe and strict synthesis conditions, complicated by high temperature (T > 900 °C) treatments of volatile and toxic elements. In this work, a milder synthetic approach to produce 1144 materials is proposed. A simple one-step High Energy Ball Milling treatment of the pure elements is coupled to a low temperature (i.e. 600 °C) thermal treatment to produce the superconducting Ca/K-1144 material, characterized by a good degree of homogeneity and critical temperatures higher than 30 K. The results here reported demonstrate the previously excluded feasibility of a simple and easily scalable lower temperature synthesis route for a Ca/K-1144 compound. We suggest that the intimate mixing and dispersion of the starting elements promoted by the mechanochemical treatment constitutes a key factor for the successful lowering of the synthesis temperature.

Fullerene mixtures as negative electrodes in innovative Na-ion batteries

After the successful electrochemical intercalation of C60 with sodium, we report here the preparation of novel negative electrodes for Na-ion batteries composed by commercial C60:C70 mixture, this being significantly less expensive than pure fullerenes. An optimized solid-state Na-poly(ethylene oxide) electrolyte was used for the battery assembly. While pure C60 electrodes show a strong irreversible behavior after the first discharge, the peculiar disordered crystalline arrangement of C60 and C70 in the mixture, increased by a high-energy ball milling treatment, allows to improve the specific capacity at the first discharge up to 320 mAh/g, as well as the overall reversibility.

Composition dependent microstructure evolution, activation and de-/hydrogenation properties of Mg–Ni–La alloys

In this work, in order to elucidate the effect of different alloying elements on the microstructure, activation and the de-/hydrogenation kinetics performance, the Mg–20La, Mg–20Ni and Mg–10Ni–10La (wt.%) alloys have been prepared by near equilibrium solidification combined with high-energy ball milling treatment to realize the internal optimization as well as particle refinement. The results show that the microstructures of the prepared alloys are significantly refined by forming different types and sizes of intermetallic compounds. Meanwhile, the effects of LaH3 and Mg2Ni within the activated samples on de-/hydrogenation kinetics are also discussed. It is observed that the alloy containing LaH3 preserves stable hydrogenation behavior between 573 and 623 K, while the hydrogenation properties of the alloy containing Mg2Ni is susceptible to temperature. A preferable hydrogenation performance is observed in Mg–10Ni–10La alloy, which can absorb as high as 5.86 wt% hydrogen within 15 min at 623 K and 3.0 MPa hydrogen pressure. Moreover, the desorption kinetics and the desorption activation energies are evaluated to illustrate the mechanism based on improved dehydrogenation performance. The addition of proper alloying elements Ni and La in combination with reasonable processing is an effective strategy to improve the de-/hydrogenation performance of Mg-based alloys.

High-energy ball milling treatment of soybean for Bacillus thuringiensis culture media

Soybean meal has been intensively used as a substrate in culture media for several microorganisms. However, the fermentable sugar containing the soybean needs to be released from the solid matrix through different processes. Against this backdrop, the present study explores the use of high-energy ball milling as a one-step treatment method for expedited production of fermentable sugars of textured soybean. The best result is observed after only 5min of milling, obtaining 34.1 times more fermentable sugars than untreated textured soybean, and 2.5 times more than commercially used soybean meal. Notably, the textured soybean ball-milled has been used as a substrate for Bacillus thuringiensis var. kurstaki HD-73 fermentation. The cell and spore production is also compared with a standard Rowe media. The maximum cell concentration obtained in the entire fermentation process using ball-milled textured soybean media is found to be higher than the concentration obtained using the standard Rowe media. In addition, it is observed that there is a direct correlation between maximum cell production and reducing sugar concentration generated by the high-energy ball milling treatment. No fermentation inhibitors or by-products are generated during the physical treatment.

Cyclability evaluation on Si based Negative Electrode in Lithium ion Battery by Graphite Phase Evolution: an operando X-ray diffraction study

Artificial graphite (FSN) additive is employed as internal structural label for projecting cyclability of Si material native electrode in a mass ratio of Si/FSN = 1.0 in Li ion battery (LIB). Results of operando X-ray diffraction analysis on Si-FSN negative electrode in LIB demonstrate that one can evaluate the lithiation and delithiation affinity of active material by referring phase transition delay of graphite as affected by experimental splits in a formation process of LIB. We prove that a thin layer of surface amorphous structure and residual lattice strain are formed in Si by high energy ball-milling treatment. Those manipulations improve Li intercalation kinetics and thus enabling a capacity fading of less than 10% (from 1860 to 1650 mAhg−1) for Si negative electrode in 50 cycles. Of utmost importance, this study discloses a robust assessment for revealing mechanism on amorphous and strain related silicide formation and predicting cyclability of negative electrode by quantitative phase evolution rate of FSN additive in LIB.

Fabrication and characterization of WC-HEA cemented carbide based on the CoCrFeNiMn high entropy alloy

A high entropy alloy (HEA, CoCrFeNiMn) synthesized by mechanical alloying was used as the binder for the densification of WC by a pressureless high temperature procedure. Three different WC were used by modifying its microstructure with a high energy ball milling treatment. The alloy content in the HEA-WC mixture was varied from 10 to 30% vol. The microstructure and properties of the sintered composites were studied by X-ray diffraction, scanning electron microscopy and microindentation.

The effect of high-energy ball milling on the electromechanical strain properties of Bi-based lead-free relaxor matrix ferroelectric composite ceramics

The crystal structure, ferroelectric, and electric-field-induced strain (EFIS) properties of Bi-based lead-free ferroelectric/relaxor composite materials are investigated. Bi1/2(Na0.82K0.18)1/2TiO3 as a ferroelectric material and 0.98Bi1/2(Na0.78K0.22)1/2TiO3‒0.02LaFeO3 as a relaxor were synthesized via conventional ceramic processing routes while the relaxor (matrix phase) was prepared via high-energy ball milling (HEBM) after calcination. The average particle size was decreased via HEBM treatment. As a result, a high d33* value of over 600pm/V was obtained at 4kV/mm for 30-min HEBM-treated composites. This demonstrates that HEBM treatment is effective in enhancing the strain properties of lead‒free piezoelectric composite materials.

Effect of preparation and processing conditions on UV absorbing properties of hydroxyapatite-Fe2O3 sunscreen

The development of innovative, safe and non-photocatalytic sunscreens is urgently needed, as it is essential to have sunscreen filters offering appropriate UV protection without damaging the environment and/or generating free radicals when in contact with the skin.Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) when substituted with iron has UV protection properties and is not photocatalytic; HAp was used to make a sunscreen filter by treating cod fish bones in an iron-containing solution, and then calcining them at 700°C. Here we present a systematic and advanced study on this material, to obtain a sunscreen with improved UV absorbing properties. Bones were treated with three different iron salts - Fe(II) chloride, Fe(II) lactate and Fe(III) nitrate - under various pH conditions.Results showed that Fe(II) chloride in basic pH led to the most effective iron inclusion. High energy ball milling or ultrasound were investigated to increase surface area and corresponding UV absorption; high energy ball milling treatment led to the best optical properties.The optimum powders were used to formulate UV protection creams, which showed Sun Protection Factor (SPF) values significantly superior to the control cream (up to 4.1). Moreover the critical wavelength (λcrit) was >370nm (388–389nm) and UVA/UVB ratios were very close to 1. With these properties these sunscreens can be classified as broad UV protectors.Results also showed that combining these powders with other sunscreens (i.e. titanium dioxide), a synergic effect between the different components was also observed. This investigation showed that HAp-based sunscreens of marine origin are a valid alternative to commercial products, safe for the health of the customers and, being non-photocatalytic, do not pose a threat to the environment.

Transformation of Goethite to Hematite Nanocrystallines by High Energy Ball Milling

α-Fe2O3nanocrystallines were prepared by direct transformation via high energy ball milling treatment forα-FeOOH powder. X-ray diffraction, Rietveld analysis, TEM, and vibrating sample magnetometer (VSM) are used to characterize the samples obtained after several milling times. Phase identification using Rietveld analysis showed that the goethite is transformed to hematite nanocrystalline after 40 hours of milling. HRTEM confirm that the obtained phase is mostly a single-crystal structure. This result suggested that the mechanochemical reaction is an efficient way to prepare some iron oxides nanocrystallines from raw materials which are abundant in the nature. The mechanism of the formation of hematite is discussed in text.

Synthesis of Ultrafine Mesoporous Tungsten Carbide by High-energy Ball Milling and Its Electrocatalytic Activity for Methanol Oxidation

Ultrafine mesoporous tungsten carbide (WC) was prepared from as-synthesized mesoporous WC using high-energy ball milling treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption techniques were used to characterize the samples. Brunauer-Emmett-Teller (BET) surface areas of WC samples increased with the increasing ball milling time and kept constant at 10–11 m2·g−1 for over 9 h. The electrocatalytic properties of methanol electro-oxidation at WC powder microelectrodes were investigated by cyclic voltammetry, chronoamperometry, and quasi-steady-state polarization techniques. The results reveal that ball-milled WC exhibits higher activity for methanol electro-oxidation than as-synthesized mesoporous WC. The suitability of ball-milled WC for methanol electro-oxidation is better than platinum (Pt) micro-disk, although the current peak is not as high as the Pt micro-disk. Moreover, increasing the methanol concentration and reaction temperature promotes methanol electro-oxidation on ultrafine mesoporous WC.

Enhancement in Piezoelectric Properties of PZT-Based Ceramics by High Energy Ball-Milling Treatment of Solid-State Synthesized Powders

The effects of high energy ball-milling (HEBM) on the sintering behavior and piezoelectric properties of 0.1 wt% <TEX>$Li_2CO_3$</TEX> doped 0.8Pb(<TEX>$Mg_{1/3}Nb_{2/3}$</TEX>)<TEX>$O_3$</TEX>-0.2Pb(<TEX>$Zr_{0.475}Ti_{0.525}$</TEX>)<TEX>$O_3$</TEX> (PMN-PZT) ceramics were investigated. It was found that HEBM treatment was quite effective to reduce the average particle size down to 300 nm, leading to increased density as well as enhanced piezoelectric properties of a sintered specimen even though prolonged HEBM resulted in unwanted secondary phases that caused a degradation of piezoelectric properties. The dielectric constant (<TEX>$\varepsilon_r$</TEX>), piezoelectric coupling factor (<TEX>$k_p$</TEX>) and piezoelectric constant <TEX>$d_{33}$</TEX> of 0.1 wt% <TEX>$Li_2CO_3$</TEX> doped PMN-PZT ceramics prepared via HEBM for 10 h reached 2040, 0.68 and 554 pC/N, respectively.

고에너지 볼 밀링을 이용한 (K0.44Na0.52)(Nb0.86Ta0.10)-0.04LiSbO3무연 압전 세라믹스의 특성

Lead-free (K 0.44 Na 0.52 )(Nb 0.86 Ta 0.10 )-0.04LiSbO₃ piezoelectric ceramics have been synthesized by conventional sintering process and then investigated on the sintering and piezoelectric properties by high energy ball milling (HEBM) treatment. The powders milled for different time are characterized by XRD, FE-SEM. The powders are pressed into a pellet and sintered. It is found that the piezoelectric properties of sintered specimens are strongly dependent on the milling time. The piezoelectric properties are enhanced by high energy ball milling treatment. The planer electromechanical coupling factor (kp) and piezoelectric constant (d 33 ) of a specimen sintered at 1050℃ are 0.44 and 267 pC/N, respectively.

Increased dissolution of ilmenite induced by high-energy ball milling

High-energy ball milling treatment leads to full dissolution of natural ilmenite sands containing both FeTiO 3 and Fe 2 Ti 3 O 9 phases in a sulphuric acid solution at 100°C. The ilmenite material has been milled for various times in two environments (vacuum and air), and characterised by X-ray diffraction, Mössbauer spectroscopy and surface area analysis. It is found that after milling for only 10 h, 50% of the sample can be dissolved as a result of the increased surface area, nanocrystalline structure and high level of lattice distortion present in the milled sample. Complete dissolution of the ilmenite is obtained on extended milling (200 h) in an oxygen free atmosphere. This occurs as a result of a gradual reduction of the Fe 3+ phase (Fe 2 Ti 3 O 9 ) to the relatively more soluble Fe 2+ phase (FeTiO 3 ) on milling in vacuum. The results overall show that the chemical reactivity of milled materials can be affected significantly by the milling conditions and environment.