Ball-milled Samples Research Articles

Glass transition kinetics in ball milled amorphous GaxTe100‐x nanoparticles

We report the glass transition kinetics in ball milled amorphous GaxTe100‐x (x=3, 6, 9 and 12) nanoparticles. From field emission scanning electron microscopic investigation, it is observed that ball milled samples of a-GaxTe100‐x contain high yield of nanoparticles with their diameter in the range of 20-40nm. X-ray diffraction patterns of these samples suggest that these nanoparticles are amorphous in nature. Glass transition kinetics of these amorphous nanoparticles shows that the values of glass transition temperature increase with the increase in composition and heating rate. The activation energy for structural relaxation calculated by two methods shows good agreement with each other and is found to increase with increasing gallium concentration, which can be explained in terms of change in chemical bonding at higher concentrations.

Molecular Dynamics, Physical Stability and Solubility Advantage from Amorphous Indapamide Drug

This study for the first time investigates physicochemical properties of amorphous indapamide drug (IND), which is a known diuretic agent commonly used in the treatment of hypertension. The solid-state properties of the vitrified, cryomilled and ball-milled IND samples were analyzed using X-ray powder diffraction (XRD), mass spectrometry, nuclear magnetic resonance (NMR), infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). These analytical techniques enabled us (i) to confirm the purity of obtained amorphous samples, (ii) to describe the molecular mobility of IND in the liquid and glassy state, (iii) to determine the parameters describing the liquid-glass transition i.e. Tg and dynamic fragility, (iv) to test the chemical stability of amorphous IND in various temperature conditions and finally (v) to confirm the long-term physical stability of the amorphous samples. These studies were supplemented by density functional theory (DFT) calculations and apparent solubility studies of the amorphous IND in 0.1 M HCl, phosphate buffer (pH=6.8), and water (25 and 37 °C).

Improving particle size distribution and flow properties of milk chocolate produced by ball mill and blending

Chocolate mass is produced by roller refining and conching or alternatively by ball milling. Grinding can generate varying particle size distributions (PSD), which again influence flow parameters. The latter are very important for downstream processing as well as mouthfeel and consumer acceptance of the final product. The objective of the work was to influence and control PSD and flow properties of ball mill chocolate. Various milk chocolate samples were produced in laboratory and pilot scale, and their PSD and flow properties were measured. First, it was tried to pre-grind milk and cocoa particles to very small size and then to produce coarser sugar particles in order to achieve a bimodal PSD. This should increase package density, which makes more fat available for the flow process. The attempt did not work very well for various practical reasons. Secondly, when instead fine and coarse fractions of the same particle composition were blended, it was possible to achieve bimodal PSDs as they are known from roller-refined products. The lowest values for flow parameters were achieved with a mix of 63 % coarse and 37 % fine particles as predicted in the literature. Thirdly, it was tested to blend roller-refined and ball-milled samples. It was possible to use one-third of the latter without considerably changing flow properties. This opens up various practical possibilities for the industry, e.g. line extension and productivity increase with relatively little effort and investment.

Hydrogenation and microstructural properties of hydriding combustion synthesized Mg-Ni-C composite ball-milled with NbF5 catalyst

Abstract The present investigation evaluates the effect of milling the hydriding combustion synthesized (HCSed) MgNiC composite with NbF5 catalyst. X-ray analysis revealed that h-Mg-(1 0 1) peak positions of the ball-milled samples shifted by an amount that varied with the milling time. Morphologically, among the SPEX ball-milled samples the samples with the NbF5 catalyst showed slightly delayed refinement/agglomeration with milling time which was attributed to lubricating-behavior of NbF5 during milling. The final products from both (planetary and SPEX) ball mills showed insignificant agglomeration. A general trend of decreasing surface area with increasing milling time was observed. The HCSed sample manually mixed with catalyst showed the largest surface area of 23.78 m2/g. The presence of the catalyst and different interfaces, such as Mg–Nb, Mg–Ni and Mg–CNTs, in the samples played a crucial role in decreasing the thermal constraints for dehydrogenation. Analysis of hydrogenation kinetics revealed that the catalyst added samples requires activation and can be easily activated. By relating the hydrogenation kinetic data with the JMAK model, the value of the reaction order, n, was found to be close to 1 for all the samples, suggesting a possible diffusional phase transition. The lowest activation energy observed in synthesized sample for hydrogenation was 64.9 kJ/mol.

Dependence of thermoelectric behaviour on severe plastic deformation parameters: A case study on p-type skutterudite DD0.60Fe3CoSb12

High-pressure torsion (HPT), a severe plastic deformation technique, can effectively improve the thermoelectric performance of skutterudites, resulting in ZT values higher than for ball-milled and hot-pressed (BMHP) samples. In this paper the influence of the HPT parameters, i.e. the number of revolutions (equivalent to the applied strain), the processing temperature and the hydrostatic pressure on the microstructural and thermoelectric properties of the skutterudite DD0.60Fe3CoSb12 are evaluated and compared with the BMHP samples before HPT processing. Whilst the three parameters have specific effects on (i) the crystallite size, (ii) the density of lattice defects and (ii) the density of cracks, a suitable combination thereof allows for an increase of the figure of merit by at least 20%.

Effects of rare-earth oxide catalysts on the ignition and combustion characteristics of boron nanoparticles

Boron is a potential choice as a fuel additive, especially for biofuels, because it has a high volumetric heating value among different practical metal additives. Although theoretically it can yield a great amount of energy upon complete combustion, its combustion is retarded by the initial presence of boron oxide which coats the particle surface. The present study deals with an experimental investigation of the ignition and combustion behaviors of boron and ball-milled samples of boron and rare earth oxide catalysts in an ethanol spray flame. Commercial boron nanoparticles and both commercial and synthesized ceria-based catalysts have been used for this study. A simple ball-milling technique was employed to prepare the catalyst coated samples, and this technique can be easily adapted for production of large batches. It was observed that the addition of nano-sized catalyst particles to boron nanoparticles improved the ignition characteristics (significant reduction in ignition delay) of the boron. Three different percentages of catalyst loading were tested to determine the effects of catalyst loading on both the ignition behavior of the boron and the primary combustion reaction. Analysis of BO2∗ emissions and of the exiting particles confirmed complete boron combustion in the combustor geometry. The nanoparticles containing ceria demonstrated improvements in both boron ignition (reduced ignition delay time) and (less significantly) the ethanol combustion.

XRD and HRTEM characterization of mechanosynthesized Ti0.9W0.1C cermet

Elemental powder mixture of titanium, tungsten and graphite is milled by high energy planetary ball mill at a fixed ball to powder mass ratio (BPMR) for different duration to produce nanosized particles of Ti0.9W0.1C hard metal. Microstructure characterization in terms of lattice imperfections and phase quantification of ball-milled samples has been done primarily by analyzing the XRD pattern and employing Rietveld method of structure and microstructure refinement. After 8h of ball-milling full formation of Ti0.9W0.1C is noticed without any contamination of other phase or milling media. TEM study of 8h ball-milled sample gives direct supportive evidence of structural and microstructural evaluation by XRD pattern analysis. A comparative study of microstructural changes between TiC and Ti0.9W0.1C helps to understand the effect of addition of W as solute in Ti–C metal matrix.

Erratum to: Investigation of phase composition and nanoscale microstructure of high-energy ball-milled MgCu sample

Erratum to: Investigation of phase composition and nanoscale microstructure of high-energy ball-milled MgCu sample

High-Pressure Torsion to Improve Thermoelectric Efficiency of Clathrates?

High-pressure torsion (HPT), as a technique to produce severe plastic deformation, has been proven effective to improve the thermoelectric performance of skutterudites. In this report, we present microstructural and thermoelectric properties of the clathrate Ba8Cu3.5Ge41In1.5 processed by HPT. The sample was synthesized from high-purity elements, subsequently annealed, ball milled, and hot pressed, and finally subject to HPT. Compared with the ball-milled and hot-pressed sample, the HPT-processed sample has higher electrical resistivity and Seebeck coefficient, and lower thermal conductivity, electron concentration, and mobility, which is attributed to the reduced grain size and increased density of dislocations, point defects, and cracks. No essential improvement of the dimensionless thermoelectric figure of merit is observed in the investigated temperature range, questioning the universal versatility of this technique for improvement of thermoelectric materials.

Effect of metal ion and ball milling on the electrochemical properties of M0.5TiOPO4 (M = Ni, Cu, Mg)

Various metal titanium oxyphosphates, M0.5TiOPO4 (M=Ni, Cu, Mg) were synthesized via modified solution route synthesis. The as synthesized M0.5TiOPO4 (M=Ni, Cu, Mg) were electrochemically tested using galvanostatic cycling, cyclic voltammetry, and rate performance measurements in order to investigate the effect of metal ion (M) on the electrochemical performance of this family of materials. All the studied materials reacted with 3 Li+ during the 1st lithiation showing reaction plateaus at different potentials versus Lithium. Similar studies were performed on M0.5TiOPO4 (M=Ni, Cu, Mg) samples with smaller particle size, obtained via ball milling, in order to understand the effect of particle size on the electrochemistry of the materials. The ball milled samples delivered higher specific charge during the 1st cycle showing reaction plateaus at different potentials, poorer capacity retention, and poorer rate capability as compared to the as synthesized ones. This was attributed to a change in morphology and particle size of the samples upon ball milling. Amongst all the tested materials, the as synthesized Cu0.5TiOPO4 showed the best electrochemistry. The ball milled Mg0.5TiOPO4 reacted with ∼5.5 Li+ during 1st lithiation (as compared to 3 Li+ expected from this family of compounds) and 3.3 Li+ during the 1st delithiation (rather than the expected 2 Li+). This suggests a reaction mechanism where Mg0.5TiOPO4 undergoes a phase transformation forming Mg0, which reversibly alloys with 2.5 extra Li+. Thus the electrochemical cycling of Mg0.5TiOPO4 gives insights into the reaction mechanism in this family of materials.

One step quickest mechanosynthesis of nanocrystalline Ti0.9Si0.1C and its microstructure characterization

Nanocrystalline Ti0.9Si0.1C has been prepared by ball-milling the elemental stoichiometric mixture of Ti, Si and graphite powders at room temperature under argon atmosphere. Microstructure characterization and quantitative estimation of different phases present in the unmilled and ball milled samples are done by analyzing the XRD patterns employing the Rietveld’s powder structure refinement method. The results reveal that formation of Ti0.9Si0.1C is initiated just after 44min of milling and full formation of stoichiometric Ti0.9Si0.1C without any contamination is achieved within 3h. To study the effect of ball milling on different microstructure parameters milling is continued up to 12h which results in a reduction of particle size to ∼9nm. Direct microstructure characterization of 12h milled sample by HRTEM corroborates the structural and microstructural evolution by indirect method using XRD data.

Structural and spectroscopic characterization of potassium fluoroborohydrides

Mechanochemical reactions between KBH4 and KBF4 result in the formation of potassium fluoroborohydrides K(BH(x)F(4-x)) (x = 0-4), as determined by (11)B and (19)F solid state NMR. The materials maintain the cubic KBH4 structure. Thermogravimetric (TG) data for a ball-milled sample with KBH4 : KBF4 = 3 : 1 are consistent with only desorption of hydrogen.

Microstructural changes and effect of variation of lattice strain on positron annihilation lifetime parameters of zinc ferrite nanocomposites prepared by high enegy ball-milling

Zn-ferrite nanoparticles were synthesized at room temperature by mechanical alloying the stoichiometric (1:1 mol%) mixture of ZnO and α-Fe2O3 powder under open air. Formation of both normal and inverse spinel ferrite phases was noticed after 30 minutes and 2.5 hours ball milling respectively and the content of inverse spinel phase increased with increasing milling time. The phase transformation kinetics towards formation of ferrite phases and microstructure characterization of ball milled ZnFe2O4 phases was primarily investigated by X-ray powder diffraction pattern analysis. The relative phase abundances of different phases, crystallite size, r.m.s. strain, lattice parameter change etc. were estimated from the Rietveld powder structure refinement analysis of XRD data. Positron annihilation lifetime spectra of all ball milled samples were deconvoluted with three lifetime parameters and their variation with milling time duration was explained with microstructural changes and formation of different phases with increase of milling time duration.

Intermartensitic Transformation in Ni54.8Mn23.2Ga21.7 Ferromagnetic Shape Memory Alloy Nano Powder

The Ni-Mn-Ga Ferromagnetic shape memory alloys are becoming an important element of sensor and actuator materials due to their large magnetic-field-induced strain and shape memory effect in recent years. The martensitic transformation temperature of the Heusler alloy system has been intensively studied. The Ni54.8Mn23.2Ga21.7 irregular agglomerated nanoparticles were prepared by ball milling method, and characterized by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy techniques. These particles reveal a disordered non modulated face centered tetragonal structure. For the first time, nanopowder has been found to undergo a sequence of temperature-induced intermartensitic transformation in addition to the martensitic transformation on cooling. It is believed that relaxation of internal stresses is the main issue in this case. The resistivity of the material has been measured on cooling from 450 K to 300 K. It is observed that the resistivity is maximum in the nano crystalline state and it decreases substantially with decrease of the temperature. Both amorphous and nanocrystalline material coexisted in the ball-milled sample, such a nanomagnetic structure is considered to be ideal for soft nanomagnetic material.

Influence of cation disorder on the magnetic properties of ball-milled ilmenite (FeTiO3)

We have investigated the evolution of crystal structure, cation disorder and magnetic properties of ilmenite (FeTiO3) after increasing time of high-energy ball-milling in an inert atmosphere. Refinement of X-ray diffraction data show that the hexagonal crystal structure of ilmenite is maintained after high-energy ball-milling of up to 128 h, but neutron diffraction studies reveal significant cation redistribution of Fe2+ and Ti4+ ions in the ball-milled samples. Mössbauer spectroscopy studies show that the magnetic hyperfine field of Fe2+, which is around 5 T before ball-milling, increases, and after milling times longer than 4 h a broad distribution of hyperfine fields with values up to around 40 T for Fe2+ is seen. This can be explained by the cation disorder induced by the ball-milling which affects the orbital contribution to the magnetic hyperfine field. In contrast to some ball-milled spinel ferrites, the Néel temperature of ilmenite is not significantly affected by the cation disorder.

Investigation of phase composition and nanoscale microstructure of high-energy ball-milled MgCu sample

The ball milling technique has been successfully applied to the synthesis of various materials such as equilibrium intermetallic phases, amorphous compounds, nanocrystalline materials, or metastable crystalline phases. However, how the phase composition and nanoscale microstructure evolute during ball milling in various materials is still controversial due to the complex mechanism of ball milling, especially in the field of solid-state amorphization caused by ball milling. In the present work, the phase evolution during the high-energy ball milling process of the Mg and Cu (atomic ratio is 1:1) mixed powder was investigated. It was found that Mg firstly reacts with Cu, forming the Mg2Cu alloy in the primary stage of ball milling. As the milling time increases, the diffracted peaks of Mg2Cu and Cu gradually disappear, and only a broad halo peak can be observed in the X-ray diffraction pattern of the final 18-h milled sample. As for this halo peak, lots of previous studies suggested that it originated from the amorphous phase formed during the ball milling. Here, a different opinion that this halo peak results from the very small size of crystals is proposed: As the ball milling time increases, the sizes of Mg2Cu and Cu crystals become smaller and smaller, so the diffracted peaks of Mg2Cu and Cu become broader and broader and result in their overlap between 39° and 45°, at last forming the amorphous-like halo peak. In order to determine the origin of this halo peak, microstructure observation and annealing experiment on the milled sample were carried out. In the transmission electron microscopy dark-field image of the milled sample, lots of very small nanocrystals (below 20 nm) identified as Mg2Cu and Cu were found. Moreover, in the differential scanning calorimetry curve of the milled sample during the annealing process, no obvious exothermic peak corresponding to the crystallization of amorphous phase is observed. All the above results confirm that the broad halo diffracted peak in the milled MgCu sample is attributed to the overlap of the broadened peaks of the very small Mg2Cu and Cu nanocrystalline phase, not the MgCu amorphous phase. The whole milling process of MgCu can be described as follows: .

Comparison of Synthesized Micro- and Nanostructure Hydroxyapatite for EPR Dosimetry

Two types of heat-treated and nonheat-treated synthetic hydroxyapatite samples were prepared. Another set of nonheat-treated sample were subjected to planetary ball mill system to obtain a sample with smaller grain sizes. The samples were irradiated in absorbed dose range of 7–45 kGy using 60Co gamma-ray source. Subsequently, the samples were subjected to electron paramagnetic resonance (EPR) measurement at room temperature in air. Signal intensities of hydroxyapatite samples have been measured, normalized to the sample mass, and were compared with bone powder samples in high-dose level from dosimetric point of view. The EPR response of ball-milled sample is higher in comparison to the one before ball milling for several times due to the great difference in particle size of the samples. The changes occurred in the structure of the heat-treated sample due to the effect of temperature do not influence the EPR response of the sample. The stability study of the EPR signal intensities were also made for all the hydroxyapatite samples.

One-step mechanosynthesis of nano structured Ti(CxN1−x) cermets at room temperature and their microstructure characterization

Nano structured Ti(Cx,N1−x) (x = 0.1–0.5 mol fraction) cermets are prepared at room temperature in a single step by ball-milling the stoichiometric mixtures of elemental α-Ti and graphite powders under nitrogen atmosphere. Within 1 h of milling (for x = 0.1), the α-Ti (hcp) phase partially transformed to metastable β-Ti (cubic) phase and the initiation of Ti(Cx,N1–x) (fcc) phase is noticed. Complete formation of Ti(C0.1N0.9) composition is observed after 5 h of milling and the other compositions are formed within 7 h of milling without any contamination either from the starting ingredients or from the milling media. Microstructure characterization of all unmilled and ball-milled powders is made by analyzing their respective X-ray diffraction (XRD) patterns employing the Rietveld structure refinement method. The microstructure of ball-milled samples is also characterized by high resolution transmission electron microscope (HRTEM). These analyses reveal the inclusion of both C and N atoms into the α-Ti lattice and confirm the average particle size of almost monodispersed spherical particles of Ti(Cx,N1–x) is ∼4 nm. The final compositions are also verified by energy dispersive X-ray (EDX) elemental analysis. Ti(Cx,N1–x) cermets are insulators and their optical band gap increases continuously from ∼4.58–5.38 eV with increasing C concentrations.

Improving electrochemical properties of spinel lithium titanate by incorporation of titanium nitride via high-energy ball-milling

Li4Ti5O12/TiN nanocomposites are fabricated through high-energy ball-milling of the mixture of spinel lithium titanate and TiN powder with different mass ratios of 100:1, 100:2, 100:4, and 100:8 (resultant nanocomposites are denoted as LTO–TiN-1B, LTO–TiN-2B, LTO–TiN-4B, and LTO–TiN-8B). All ball-milled samples exhibit markedly improved electrochemical properties than pristine Li4Ti5O12. Particularly, LTO–TiN-2B electrode has a high capacity of 130 mA h g−1 at a charge/discharge rate of 20C and the capacity retention was 85% after 1000 cycles at 10C, showing the best electrochemical performance and great potential as an anode material for high-rate lithium-ion batteries. The transmission electron microscopy and X-ray diffraction results indicate that amorphous TiN is generated on the surface of LTO. The improved electrochemical performance may be attributed to TiN which can significantly enhance the electronic conductivity of the nanocomposites.

Magnetic and magnetocaloric properties of ball milled Nd5Ge3

Effect of particle size reduction of the intermetallic compound Nd5Ge3 by ball milling has been studied by investigating the change in the magnetic and magnetocaloric properties. Ball milling is found to enhance the strength of the ferromagnetic component. An analysis based on the Arrott plots shows clear difference in the critical exponents between the bulk and the ball milled samples. Though the maximum entropy change and the relative cooling power are not altered much by the size reduction, magnetic transition temperature is affected.