Effect Of High Energy Ball Milling Research Articles

Charge Storage Properties of Ferrimagnetic BaFe12O19 and Polypyrrole-BaFe12O19 Composites.

This investigation is motivated by an interest in multiferroic BaFe12O19 (BFO), which combines advanced ferrimagnetic and ferroelectric properties at room temperature and exhibits interesting magnetoelectric phenomena. The ferroelectric charge storage properties of BFO are limited due to high coercivity, low dielectric constant, and high dielectric losses. We report the pseudocapacitive behavior of BFO, which allows superior charge storage compared to the ferroelectric charge storage mechanism. The BFO electrodes show a remarkably high capacitance of 1.34 F cm-2 in a neutral Na2SO4 electrolyte. The charging mechanism is discussed. The capacitive behavior is linked to the beneficial effect of high-energy ball milling (HEBM) and the use of an efficient dispersant, which facilitates charge transfer. Another approach is based on the use of conductive polypyrrole (PPy) for the fabrication of PPy-BFO composites. The choice of new polyaromatic dopants with a high charge-to-mass ratio plays a crucial role in achieving a high capacitance of 4.66 F cm-2 for pure PPy electrodes. The composite PPy-BFO (50/50) electrodes show a capacitance of 3.39 F cm-2, low impedance, reduced charge transfer resistance, enhanced capacitance retention at fast charging rates, and good cyclic stability due to the beneficial effect of advanced dopants, HEBM, and synergy of the contribution of PPy and BFO.

Rare-Earth Ion Loss of Er- or Yb-Doped LiNbO3 Crystals Due to Mechanical Destructive Effect of High-Energy Ball Milling

Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.

Effect of mechanical milling on microstructure evolution and mechanical properties of Al–Zn–Mg–Cu–Si alloy fabricated via spark plasma sintering

We investigated the effect of high-energy ball milling (HEBM) on the microstructure and mechanical properties of powders and spark plasma sintered samples of an Al–Zn–Mg–Cu–Si alloy. HEBM produced a nanocrystalline powder with an average grain size of 0.16 μm while increasing the amount of solid solution and the formation of fine amorphous aluminium oxide. The sintered alloy without HEBM consisted of η-Mg(Zn,Cu,Al)2, T-Mg32(Al,Zn)49, β-Mg2Si, and Q-Al5Cu2Mg8Si6 phases. The grain size of the sintered alloy decreased from 2.66 to 0.40 μm due to the application of HEBM. The amorphous aluminium oxide phase in the milled powder was transformed into MgO particles during sintering. The formation of MgO particles caused the depletion of Mg solid solutions, which resulted in the formation of Mg-free phases during sintering. High-energy ball milling (HEBM) improved the microhardness of the sintered alloy from 94 to 134 HV owing to grain refinement and the formation of fine secondary phases and MgO particles.

Effect of High-Energy Ball Milling Time on the Density and Mechanical Properties of W-7%Ni-3%Fe Alloy

The present work was aimed at the investigation of the effect of high-energy ball milling (HEBM) time on the sintering kinetics, structure, and properties of the heavy tungsten alloy (HTA) W-7%Ni-3%Fe. The HTA samples were obtained from nanopowders (20–80 nm) using conventional liquid-phase sintering (LPS) in hydrogen and using spark plasma sintering (SPS) in vacuum. The HTA density was shown to depend non-monotonously on the HEBM time that originates from the formation of nonequilibrium solid solutions in the W-Ni-Fe systems during HEBM. The SPS kinetics of the HTA nanopowders was shown to have a two-stage character, the intensity of which depends on the Coble diffusion creep rate and on the intensity of diffusion of the tungsten atoms in the crystal lattice of the γ-phase. The kinetics of sintering of the initial submicron powders has a single-stage character originating from the intensity of the grain boundary diffusion in the γ-phase. The dependencies of the hardness and of the yield strength on the grain sizes were found to obey the Hall–Petch relation. The hardness, strength, and dynamic strength in the compression tests of the fine-grained tungsten alloys obtained using SPS and LPS were studied.

Effect of High-Energy Ball Milling in Ternary Material System of (Mg-Sn-Na)

In this study, the nature of the ball-milling mechanism in a ternary materials system (Mg-6Sn-1Na) is investigated for proper mechanical alloying. An identical powder mixture for this material system is exposed to different milling durations for a suitable mixture. First, the platelet structure formation is observed on particles with increasing milling duration, mainly formed in <200> direction of the hexagonal crystal structure of the Mg matrix. Then, the flake structure with texture formation is broken into smaller spherical particles with further ball milling up to 12 h. According to EDS analysis, the secondary phases in the Mg matrix are homogenously distributed with a 12-h milling duration which advises a proper mixture in this material system. The solid solution formation is triggered with an 8-h milling duration according to XRD analysis on 101 reflections. Conventional sintering is performed at 350 °C in 2 h for each sample. In bulk samples, XRD data reveal that secondary phases (Mg2Sn) with island-like structures are formed on the Mg matrix for a milling duration of up to 8 h. These bigger secondary phases are mainly constituted as Mg2Sn intermetallic forms, which have a negative effect on physical and mechanical properties due to a mismatch in the grain boundary formation. However, the homogenous distribution of secondary phases with a smaller particle size distribution, acquired with 12 h milling time, provides the highest density, modulus of elasticity, and hardness values for this ternary materials system. The ternary materials produced with the 12-h ball-milling process provide an improvement of about 117% in hardness value compared with the cast form.

Increasing sinterability and ionic conductivity of Na3Zr2Si2PO12 ceramics by high energy ball-milling

Na3Zr2Si2PO12 (NZSP) is one of the most promising solid electrolytes for all-solid-state sodium-ion batteries. In this work, NZSP was obtained using the mechanochemically assisted solid-state route. The effect of high-energy ball milling (HEBM) on sintering and conductive properties of as-prepared NZSP was shown. It was mentioned that the polydisperse particle size distribution of HEBM samples has a positive effect on densification during the pressing, which enables using low pressure (10 MPa). High-density ceramics (3.14 g∙cm−3) with high ionic conductivity (2.12∙10−3 S∙cm−1) and low activation energy (0.31 eV) was obtained after 10 min of HEBM. The value of the electronic conductivity obtained from the analysis of DC polarization using blocking Au electrodes is equal to 4.85∙10−9 S∙cm−1. The NZSP ceramics shows stability during the charge-discharge process at a current density of 0.1 mA∙cm−2 for 200 h at room temperature. The transference number of Na+ ions is 0.95 and practically does not change during cycling. The high ionic conductivity, exceeding 10−3 S∙cm−1, is confirmed by measuring ionic conductivity at AC and DC current.

Effect of high-energy ball milling on the microstructure and mechanical properties of Ni-based ODS alloys fabricated using gas-atomized powder

Effect of high-energy ball milling on the microstructure and mechanical properties of Ni-based ODS alloys fabricated using gas-atomized powder

Influence of High Energy Ball Milling and Dispersant on Capacitive Properties of Fe2O3—Carbon Nanotube Composites

This investigation is motivated by increasing interest in ferrimagnetic materials and composites, which exhibit electrical capacitance. It addresses the need for the development of magnetic materials with enhanced capacitive properties and low electrical resistance. γ-Fe2O3-multiwalled carbon nanotube (MWCNT) composites are developed by colloidal processing and studied for energy storage in negative electrodes of supercapacitors. High energy ball milling (HEBM) of ferrimagnetic γ-Fe2O3 nanoparticles results in enhanced capacitive properties. The effect of HEBM on particle morphology is analyzed. Gallocyanine is used as a co-dispersant for γ-Fe2O3 and MWCNTs. The polyaromatic structure and catechol ligand of gallocyanine facilitated its adsorption on γ-Fe2O3 and MWCNTs, respectively, and facilitated their electrostatic dispersion and mixing. The adsorption mechanisms are discussed. The highest capacitance of 1.53 F·cm−2 is achieved in 0.5 M Na2SO4 electrolyte for composites, containing γ-Fe2O3, which is high energy ball milled and co-dispersed with MWCNTs using gallocyanine. HEBM and colloidal processing strategies allow high capacitance at low electrical resistance, which facilitates efficient charge–discharge. Obtained composites are promising for fabrication of multifunctional devices based on mutual interaction of ferrimagnetic and capacitive properties.

Effect of high-energy ball milling on the microstructure, phase composition and microhardness of the Al–Mn–Cu alloy

   X-ray diffraction and scanning electron microscopy methods were used to study the effect of the planetary ball mill treatment time on the morphology, phase composition and microstructure of the Al–Mn–Cu-based alloy granules with and without nanodiamond particles. The phase composition of the alloy was determined by X-ray diffraction after casting and milling for 5–20 h. It was shown that nanodiamond particles promote granule coarsening, and this is especially noticeable with an increase in the milling time up to 20 h. At the same time, the size of initial alloy granules weakly depends on the processing time. Cu-bearing phases of crystallization origin dissolve during mechanical alloying. The lattice constant of the aluminum solid solution decreases after 5-hour treatment to 0.4028–0.4030 nm, and increases with further increasing milling time. Exothermic effects associated with the precipitation of secondary phases were revealed for mechanically alloyed granules during heating. An increase in the milling time reduces the intensity of peaks. The solidus temperature of samples decreased after mechanical alloying. For the nanodiamond-bearing sample, an exothermic effect is observed which can be ascribed to the aluminum carbide formation or oxidation reactions in nanodiamond particles. The maximum microhardness is achieved after 5–10 h of mechanical alloying, and the nanodiamond particles slightly increase the maximum microhardness from 316 to 330 HV. The results indicate the dissolution of copper and manganese in the aluminum solid solution after 5 h of treatment and their precipitation with the increasing milling time. Nanodiamond particles have no effect on the dissolution of elements but accelerate the solid solution decomposition with the increasing treatment time.

Effect of high-energy ball-milling on the magnetostructural properties of a Ni45Co5Mn35Sn15 alloy

The effect of high-energy ball-milling on the magnetostructural properties of a Ni45Co5Mn35Sn15 alloy in austenitic phase at room temperature has been analyzed by neutron and high-resolution X-ray diffraction. The ball milling promotes a mechanically-induced martensitic transformation as well as the appearance of amorphous-like non-transforming regions, following a double stage; for short milling times (below 30 min), a strong size reduction and martensite induction occur. On the opposite, for longer times, the increase of strains predominates and consequently a larger amount of non-transforming regions appears. The effect of the microstructural defects brought by milling (as dislocations) on both the enthalpy change at the martensitic transformation and the high field magnetization of the austenite has been quantitatively estimated and correlated to the internal strains. Contrary to what occurs in ternary Ni-Mn-Sn alloys, the mechanically-induced defects do not change the ferromagnetic coupling between Mn atoms, but just cause a net reduction on the magnetic moments.

Dense HfB2 ceramics fabricated by high-energy ball milling and spark plasma sintering

The effects of high-energy ball milling (HEBM) on the sintering ability and microstructure of hafnium diboride (HfB2) ultrahigh-temperature ceramics (UHTCs) were investigated. After HEBM, the average particle size range of the HfB2 ceramics decreased to 10–20 nm with a slight alteration in the crystal structure. The microscopic grains of the sintered samples were homogeneous and fine in size. WC removed oxide impurities on the surface of the HfB2 particles by reacting with the oxide impurities, which further improved the sintering ability of the HfB2 ceramics. The densification mechanism of the HfB2 ceramics was also investigated, and nearly fully dense HfB2 (99.1%) was fabricated by reactive spark plasma sintering (R–SPS) at 2100 °C for 35 min under a pressure of 40 MPa. HEBM increased the surface energy of the fine particles, which provided a sufficient driving force to improve the sintering ability and significantly increase the densification of HfB2.

Effect of High-Energy Ball Milling on the Structural Phase State and Magnetic Properties of Boron Nitride and Iron Powder Mixtures

An investigation is performed of the effect the high-energy ball milling (mechanical alloying, MA) of a mixture of iron and hexagonal boron nitride (h-BN) powders at a component weight ratio of Fe : BN = 1 has on the phase composition and magnetic properties of the synthesized material. High-energy ball milling with subsequent annealing of the MA powder at 600°C is shown to alter its phase composition, structure, and magnetic characteristics substantially.

Effect of high-energy ball-milling on the spark plasma sinterability of ZrB2 with transition metal disilicides

A wide suite of powder mixtures of ZrB2 with five different additions of transition metal disilicides (MeSi2; 5, 17.5, or 30 vol% MoSi2; 17.5 vol% TaSi2; or 17.5 vol% ZrSi2) were prepared by high-energy ball-milling (HEBM) for different times, and their optimal densification temperatures were evaluated by dilatometric spark-plasma-sintering (SPS) tests to compare their sinterability. SPS densification tests at the so-determined optimal densification temperatures were also performed in selected cases. It was found that HEBM progressively enhanced the sinterability, especially once the ZrB2 particle sizes were refined to the ultrafine range or below (<250 nm). It was also observed that the sinterability was enhanced (i) with the greater addition of MeSi2, and (ii) with the lower refractoriness of the MeSi2. Nonetheless, under long-time HEBM, the addition of harder, more refractory MeSi2 or of softer, less refractory MeSi2 is equally effective in terms of sinterability, both enabling low-temperature densification (SPS at ∼1200 °C).

Effect of high-energy ball milling on the magnetocaloric properties of La0.7Ca0.2Sr0.1MnO3

We report an experimental–theoretical analysis of the large magnetocaloric effect observed in the compound La0.7Ca0.2Sr0.1MnO3, synthesized by high-energy ball milling assisted by heat treatment. We demonstrated that this method induces crystal structure distortions and defects, which are responsible for the excellent MC properties. X-ray diffraction and Rietveld refinement allowed quantification of the high levels of microstrain and distortion of the synthesized orthorhombic structure (Pnma). Temperature-dependent magnetization measurements reveal a Curie temperature of approximately 310 K; furthermore, a large value of magnetic entropy change |ΔSM|= 4.11 Jkg−1 K−1 and relative cooling power of 61.12 Jkg−1 were estimated by means of Maxwell's equations under an applied field (H) of 18 kOe, making this manganite a promising material for refrigeration applications. Electron paramagnetic resonance spectra of the doped manganite show the presence of Mn4+ ions, which strengthen the double-exchange interaction (ferromagnetic). It is demonstrated that the high-energy ball milling process assisted by heat treatment is an easy, economic, and fast method for synthesizing doped manganites, showing improved magnetocaloric properties compared to those of the same material synthesized by other methods.

Effect of High-Energy Ball Milling on Molten Salt Synthesized Barium Hexaferrite Powder

M-type hexagonal ferrite powder was prepared by the molten salt flux method calcined at a relatively low temperature (850 °C) with a product yield of 99.87%. The synthesized sample was then milled for 3 h by high-energy ball milling in toluene suspension to obtain ultrafine nanoparticles. The structural, morphological, and magnetic properties of the particles were investigated to observe the effect of milling on the molten salt synthesized powder. The analyses reveal the presence of barium hexaferrite (BaFe12O19) as the main phase with less impurities. Average crystallite size, determined by X-ray diffraction (XRD), decreased from 81 ± 20 nm to 52 ± 5 nm after ball milling. The Fourier transform infrared (FTIR) spectra ensure the tetrahedral and octahedral positions in barium hexaferrite structure with an increase in the intensity of absorption bands after milling. The electron paramagnetic resonance (EPR) signal shows a broad line that demonstrates a decrease in the amplitude of the milled sample. Furthermore, remanence measured by vibrating sample magnetometer (VSM) increases from 8.5 to 25 emu/g. A 72% increase in coercivity and 84% increase in magnetic saturation is observed for the milled samples compared to that of pure BaFe12O19 (unmilled). The variations of the magnetic properties are thus attributed to the reduction in crystalline size and lattice parameters after milling.

Structural, Mechanical and Dielectric Properties of Microwave-Assisted High-Energy Ball Milling Synthesis of Hydroxyapatite

In the present work, the effect of high-energy ball milling (HEBM) of starting precursors of hydroxyapatite (Ca10(PO4)6(OH)2)/HA system on the processing temperature, morphological, mechanical, and electrical properties are highlighted. Calcination and sintering of HA system were carried out in microwave furnace. XRD study confirmed the evolution of HA phase and EDX analysis confirmed Ca/P ratio ∼1.65. Grain size of HA samples, synthesized by using microwave-assisted HEBM technique was found to be in the order of 54–75 nm. Enhanced dielectric and mechanical properties were obtained in HA samples.

Processing and properties of PcBN composites fabricated by HPHT using PSN and Al as sintering additive

Dense polycrystalline cubic boron nitride (PcBN) composites were fabricated by high-pressure and high-temperature (HPHT) sintering using polysilazane (PSN) and Al as sintering additive. After high-energy ball milling, the cBN fine particles were uniformly coated with PSN by ultrasonic treatment. After thermocuring and pyrolysis, the cBN–SiCN particles were mixed with Al. The PcBN composites were prepared after sintering at 1450 °C for 10 min with a pressure of 5 GPa. The refining effect of high-energy ball milling on the cBN particles was studied by scanning electron microscopy (SEM) and laser particle size analyzer. The oxidation of the cBN particles after milling was investigated by nitrogen–oxygen analyzer. The phase composition and microstructure of the sintered PcBN composites were investigated by X-ray diffractometer (XRD) and SEM. The main phases of the sintered PcBN composites are cBN, AlN, SiC and Si3N4. The conversion of cBN to hBN was inhibited by the formation of AlN. The mechanical properties of the sintered PcBN composites were improved by the appearance of SiC and Si3N4. The density and mechanical properties of the PcBN composites both increased with the content of the cBN particles increasing. The sintered sample with 60 wt% cBN, 30 wt% PSN and 10 wt% Al showed the best results: density of 99.7%, Vickers’ hardness of (25.2 ± 0.8) GPa and flexural strength of (602 ± 15) MPa.

High-energy ball milling of lead-free piezoceramic: influence of milling medium on properties

The study highlights the effect of high-energy ball milling (HEBM) in dry and wet mode, in comparison to conventional ball milling (CBM), on NKN-based lead-free piezoceramics. The particle size reduced significantly from 1.97 μm (CBM) to 115 nm after wet HEBM which enhanced the piezoelectric property significantly. HEBM influenced the microstructure of the samples which improved the density, and the samples exhibited excellent ferroelectric character, stable ageing and electrical fatigue behaviour. As compared to CBM, dielectric constant increased nearly 50%, while piezoelectric charge coefficient (d33) increased more than double by wet HEBM. The wet HEBM samples also showed better ferroelectric properties and higher Curie temperature (~ 320 °C) along with improved resistance to thermal annealing due to stable ferroelectric polarisation state.

Formation of Amorphous Structures and Their Crystallization in the Cu–Ti System by High-Energy Ball Milling

The results of the investigation into the formation of amorphous structures in the Cu–Ti system and their subsequent crystallization under the effect of high-energy ball milling (HEBM) are presented. To form amorphous Cu–Ti powders, powders of copper (MPS-V grade with average particle size d = 45–100 μm, GOST (State Standard) 4960–75) and titanium (PM99.95, d = 2.0–4.5 μm, TU (Technical Specifications) 48-19-316–80) are selected as the initial components. The HEBM of Cu + Ti powder mixtures is performed using an Aktivator-2S laboratory planetary ball mill (at revolution rates of discs of 694 rpm and drums of 1388 rpm) for 1–30 min. The investigations into the surface morphology and micro-, nano-, and atomic crystalline structure of activated Cu + Ti powder mixtures are fulfilled by X-ray structural analysis (XSA) using a DRON-3M diffractometer, scanning electron microscopy using a Zeiss Ultra+ microscope (Germany) with the application of energy dispersive analysis, and high-resolution transmission electron microscopy (TEM) using a Titan microscope (United States). The determination of thermal characteristics of phase transformations (temperature, heat of reaction, and amorphous-to-crystalline transition) are performed by differential scanning calorimetry using a DSC 204 F1 device in the mode of linear heating to 450°C at a rate of 20 K/min. The Cu–Ti amorphous powders were fabricated using HEBM for 20 min. The XSA data evidence that the fraction of the amorphous phase in the material was 93%. The TEM investigations showed that the material preferentially consists of the amorphous phase with an insignificant content of nanocrystalline regions 2–8 nm in size. It is found that the Cu–Ti amorphous phase crystallizes in a temperature range of 336–369°C, and the heat of reaction is 79.78 J/g.

Evolution of metal nitriding and hydriding reactions during ammonia plasma-assisted ball milling

Nanocrystalline metal nitride and hydride powders were prepared using plasma-assisted ball milling in ammonia gas (NH3-P-milling) via an in situ synthesis reaction. The gas–solid reactions were triggered by a short duration of plasma milling of Mg and Ti under a constant pressure of ammonia gas, and the products in the two systems were nanocrystalline Mg3N2 and TiN, TiH2 after 10 h, respectively. During the NH3-P-milling of Ti powder, TiH2 and TiN were formed during the initial stages of milling, and then, the TiH2 decomposed during further milling upon reaction with N radicals, transforming into the TiN phase. In contrast, no chemical reaction occurred between NH3 and Mg/Ti after 10 h of C-milling. The discharge plasma activated and decomposed the ammonia gas and activated the surface of the powders, which, together with the mechanical effect of high-energy ball milling, accelerated the gas–solid reactions.