This study analyzed the influence of ball size and process control agents on the refinement and dehydrogenation behavior of TiH2 powder. Powders milled using ZrO2 balls with diameters of 0.1 mm, 0.3 mm, and 0.3+0.5+1 mm exhibited a bimodal particle size distribution, of which the first mode had the smallest size of 0.23 μm for the 0.3 mm balls. Using ethanol and/or stearic acid as process control agents was effective in particle refinement. Thermogravimetric analysis showed that dehydrogenation of the milled powder started at a relatively low temperature compared to the raw powder, which is interpreted to have resulted from a decrease in particle size and an increase in defects. The dehydrogenation kinetics of the TiH2 powder were evaluated by the magnitude of peak shift with heating rates using thermogravimetric analysis. The activation energy of the dehydrogenation reaction, calculated from the slope of the Kissinger plot, was measured to be 228.6 kJ/mol for the raw powder and 194.5 kJ/mol for the milled powder. TEM analysis revealed that both the milled and dehydrogenated powders showed an angular shape with a size of about 200 nm.

The structure and magnetic properties of composite powders prepared by ball milling a mixture of Fe2O3 ‧ (0.4-1.0)Fe were investigated. Hysteresis loops and differential scanning calorimetry (DSC) curves are used to characterize the materials and to examine the effect of the solid state reaction induced by ball milling. The results showed that a solid state reaction in Fe2O3 ‧ (0.4-1.0)Fe clearly proceeds after only 1 h of ball milling. The system is characterized by a positive reaction heat of +2.23 kcal/mole. The diffraction lines related to Fe2O3 and Fe disappeared after 1 h of ball milling and, instead, diffraction lines of the intermediate phase of Fe3O4 plus FeO formed. The magnetization and coercivity of the Fe2O3 ‧ 0.8Fe powders were changed by the solid state reaction process of Fe2O3 by Fe during ball milling. The coercivity of the Fe2O3 ‧ 0.8Fe powders increased with increasing milling time and reached a maximum value of 340 Oe after 5 h of ball milling. This indicates the grain size of Fe3O4 was clearly reduced during ball milling. The magnetic properties of the annealed powders depend on the amount of magnetic Fe and Fe3O4 phases.

This study investigated the effects of revolution speed and ball size in planetary milling on the microstructure and dehydrogenation behavior of TiH2 powder. The particle size analysis showed that the large particles present in the raw powder were effectively refined as the revolution speed increased, and when milled at 500 rpm, the median particle size was 1.47 μm. Milling with a mixture of balls of two or three sizes was more effective in refining the raw powder than milling with balls of a single size. A mixture of 3 mm and 5 mm diameter balls was the optimal condition for particle refinement, and the measured median particle size was 0.71 μm. The dependence of particle size on revolution speed and ball size was explained by changes in input energy and the number of contact points of the balls. In the milled powder, the endothermic peak measured using differential thermal analysis was observed at a relatively low temperature. This finding was interpreted as the activation of a dehydrogenation reaction, mainly due to the increase in the specific surface area and the concentration of lattice defects.

Tungsten disulfide (WS2) nanosheets have attracted considerable attention because of their unique optical and electrical properties. Several methods for fabrication of WS2 nanosheets have been developed. However, methods for mass production of high-quality WS2 nanosheets remain challenging. In this study, WS2 nanosheets were fabricated using mechano-chemical ball milling based on the synergetic effects of chemical intercalation and mechanical exfoliation. The ball-milling time was set as a variable for the optimized fabricating process of WS2 nanosheets. Under the optimized conditions, the WS2 nanosheets had lateral sizes of 500–600 nm with either a monolayer or bilayer. They also exhibited high crystallinity in the 2H semiconducting phase. Thus, the proposed method can be applied to the exfoliation of other transition metal dichalcogenides using suitable chemical intercalants. It can also be used with highperformance WS2-based photodiodes and transistors used in practical semiconductor applications.

Recently, high-entropy carbides have attracted considerable attention owing to their excellent physical and chemical properties such as high hardness, fracture toughness, and conductivity. However, as an emerging class of novel materials, the synthesis methods, performance, and applications of high-entropy carbides have ample scope for further development. In this study, equiatomic (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide powders have been prepared by an ultrahigh- energy ball-milling (UHEBM) process with different milling times (1, 5, 15, 30, and 60 min). Further, their refinement behavior and high-entropy synthesis potential have been investigated. With an increase in the milling time, the particle size rapidly reduces (under sub-micrometer size) and homogeneous mixing of the prepared powder is observed. The distortions in the crystal lattice, which occur as a result of the refinement process and the multicomponent effect, are found to improve the sintering, thereby notably enhancing the formation of a single-phase solid solution (high-entropy). Herein, we present a procedure for the bulk synthesis of highly pure, dense, and uniform FCC single-phase (Fm3m crystal structure) (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide using a milling time of 60 min and a sintering temperature of 1,600oC.

Tin/graphite composites are prepared as anode materials for Li-ion batteries using a dry ball-milling process. The main experimental variables in this work are the ball milling time (0–8 h) and composition ratio (tin:graphite=5:95, 15:85, and 30:70 w/w) of graphite and tin powder. For comparison, a tin/graphite composite is prepared using wet ball milling. The morphology and structure of the different tin/graphite composites are investigated using X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and scanning and transmission electron microscopy. The electrochemical properties of the samples are also examined. The optimal dry ball milling time for the uniform mixing of graphite and tin is 6 h in a graphite-30wt.%Sn sample. The electrode prepared from the composite that is dry-ballmilled for 6 h exhibits the best cycle performance (discharge capacity after 50th cycle: 308 mAh/g and capacity retention: 46%). The discharge capacity after the 50th cycle is approximately 112 mAh/g, higher than that when the electrode is composed of only graphite (196 mAh/g after 50th cycle). This result indicates that it is possible to manufacture a tin/graphite composite anode material that can effectively buffer the volume change that occurs during cycling, even using a simple dry ball-milling process.

The hydrogen reduction behavior of the CuO-Co3O4 powder mixture for the synthesis of the homogeneous Cu-15at%Co composite powder has been investigated. The composite powder is prepared by ball milling the oxide powders, followed by a hydrogen reduction process. The reduction behavior of the ball-milled powder mixture is analyzed by X-ray diffraction (XRD) and temperature-programmed reduction at different heating rates in an Ar-10%H2 atmosphere. The scanning electron microscopy and XRD results reveal that the hydrogen-reduced powder mixture is composed of fine agglomerates of nanosized Cu and Co particles. The hydrogen reduction kinetics is studied by determining the degree of peak shift as a function of the heating rate. The activation energies for the reduction of the oxide powders estimated from the slopes of the Kissinger plots are 58.1 kJ/mol and 65.8 kJ/mol, depending on the reduction reaction: CuO to Cu and Co3O4 to Co, respectively. The measured temperature and activation energy for the reduction of Co3O4 are explained on the basis of the effect of pre-reduced Cu particles.

Tungsten heavy alloys (W–Ni–Fe) play an important role in various industries because of their excellent mechanical properties, such as the excellent hardness of tungsten, low thermal expansion, corrosion resistance of nickel, and ductility of iron. In tungsten heavy alloys, tungsten nanoparticles allow the relatively low-temperature molding of high-melting-point tungsten and can improve densification. In this study, to improve the densification of tungsten heavy alloy, nanoparticles are manufactured by ultrasonic milling of metal oxide. The physical properties of the metal oxide and the solvent viscosity are selected as the main parameters. When the density is low and the Mohs hardness is high, the particle size distribution is relatively high. When the density is high and the Mohs hardness is low, the particle size distribution is relatively low. Additionally, the average particle size tends to decrease with increasing viscosity. Metal oxides prepared by ultrasonic milling in high-viscosity solvent show an average particle size of less than 300 nm based on the dynamic light scattering and scanning electron microscopy analysis. The effects of the physical properties of the metal oxide and the solvent viscosity on the pulverization are analyzed experimentally.

The hydrogen reduction behavior of MoO3-CuO powder mixture for the synthesis of homogeneous Mo-20 wt% Cu composite powder is investigated. The reduction behavior of ball-milled powder mixture is analyzed by XRD and temperature programmed reduction method at various heating rates in Ar-10% H2 atmosphere. The XRD analysis of the heat-treated powder at 300oC shows Cu, MoO3, and Cu2MoO5 phases. In contrast, the powder mixture heated at 400oC is composed of Cu and MoO2 phases. The hydrogen reduction kinetic is evaluated by the amount of peak shift with heating rates. The activation energies for the reduction, estimated by the slope of the Kissinger plot, are measured as 112.2 kJ/mol and 65.2 kJ/mol, depending on the reduction steps from CuO to Cu and from MoO3 to MoO2, respectively. The measured activation energy for the reduction of MoO3 is explained by the effect of pre-reduced Cu particles. The powder mixture, hydrogen-reduced at 700oC, shows the dispersion of nano-sized Cu agglomerates on the surface of Mo powders.

A Nanosized WO3 and CuO powder mixture is prepared using novel high-energy ball milling in a bead mill to obtain a W-Cu nanocomposite powder, and the effect of milling time on the structural characteristics of WO3-CuO powder mixtures is investigated. The results show that the ball-milled WO3-CuO powder mixture reaches at steady state after 10 h milling, characterized by the uniform and narrow particle size distribution with primary crystalline sizes below 50 nm, a specific surface area of 37 m2/g, and powder mean particle size (D50) of 0.57 μm. The WO3-CuO powder mixtures milled for 10 h are heat-treated at different temperatures in H2 atmosphere to produce W-Cu powder. The XRD results shows that both the WO3 and CuO phases can be reduced to W and Cu phases at temperatures over 700oC. The reduced W-Cu nanocomposite powder exhibits excellent sinterability, and the ultrafine W-Cu composite can be obtained by the Cu liquid phase sintering process.

Fe-base superalloy powders with Y2O3 dispersion were prepared by high energy ball milling, followed by sparkplasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50mm were usedfor the preparation of Fe-20Cr-4.5Al-0.5Ti-O.5Y2O3 powder mixtures (wt%). The milling process of the powders was carriedout in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation(350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) wereapplied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclicoperation and was about 15nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constantmilling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at 1100oC for 30 min invacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, ahomogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

In this research, magnesium powder was prepared by gas atomizing. Refinement behaviors of magnesium powder produced under different conditions were investigated using a mechanical milling (attrition milling) process. Analyses were performed to assess the characterization and comparison of milled powder with different steel ball sizes and milling times. The powders were analyzed by field emission scanning electron microscope, apparent density and powder fluidity. The particle morphology of the Mg powders changed from spherical particles of feed metals to irregular oval particles, then plate type particles, with an increasing milling time. Because of the HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, which results in producing plate-type powders. An increase in ball size and the impact energy of the magnesium powder maximizes the effect of refinement. Furthermore, it is possible to improve the apparent density and fluidity according to the smoothness of the surface of the initial powder.

We examined various ball-milling parameters which affect the structural and morphological modification of multi-wall carbon nanotubes. In particular, the effect of milling mode and the use of different milling agents were exam- ined. Friction milling mode induced more structural changes than impact milling mode except the use of dry ice as a milling agent. Wet milling was helpful for reducing more effectively the agglomeration of nanotubes than dry milling. The use of hard solid particles such as silica and alumina as milling agents resulted in an effective shortening of nan- otubes, but often susceptible to the amorphization and the destruction of crystallinity.

Nanocrystalline powder could be synthesized by solid-state reaction using the mixture which was prepared by a high energy milling process in a bead mill for and nanocrystalline powders mixture. Effect of the milling time on the powder characteristic of the synthesized powder was investigated. Nanocrystalline with a particle size of 50 nm was obtained at . High tetragonal powder with a tetragonality(=c/a) of 1.009 and a specific surface area of was acquired after heat-treatment at for 2 h. High energy ball milling was effective in decreasing the reaction temperature and increasing the tetragonality.

In this study, a high energy ball milling process was employed in order to improve the densification of direct nitrided AlN powder. The densification behavior and the sintered microstructure of the milled AlN powder were investigated. Mixture of AlN powder doped with 5 wt.% as a sintering additive was pulverized and dispersed up to 50 min in a bead mill with very small beads. Ultrafine AlN powder with a particle size of 600 nm and a specific surface area of 9.54 was prepared after milling for 50 min. The milled powders were pressureless-sintered at for 4 h under atmosphere. This powder showed excellent sinterability leading to full densification after sintering at for 4 h. However, the sintered microstructure revealed that the fraction of yitttium aluminate increased with milling time and sintering temperature and the newly-secondary phase of ZrN was observed due to the reaction of AlN with the impurity.

In order to make a (CZTSe) sputtering target sintered for solar cell application, synthesis of CZTSe compound by solid state reaction of Cu, Zn, Sn and Se mixed powders and effects of ball milling condition on sinterability such as ball size, combination of ball size, ball milling time and sintering temperature, was investigated. As a result of this research, sintering at after ball milling using mixed balls of 1 mm and 3 mm for 72 hours was the optimum condition to synthesis near stoichiometric composition of and to prepare sintered pellet with high density relatively.

Sm-16.7wt%Co alloy powders were prepared by high energy ball milling under the conditions of various milling time and the content of process control agent (PCA), and their microstructure and magnetic properties were investigated to establish optimum processing conditions. The initial powders employed showed irregular shape and had a size ranging from 5 to . After milling for 5 h, the shape of powders changed to round shape and their mean powder size was approximately , which consisted of the agglomerated nano-sized particles with 15 nm in diameter. The coercivity was reduced with increasing the milling time, whereas the saturation magnetization increased. As the content of PCA increased, the powder size minutely decreased to approximately at the PCA content of 10 wt%. The XRD patterns showed that the main diffraction peaks disappeared apparently after milling, indicating the formation of amorphous structure. The measured values of coercivity were almost unchanged with increasing the content of PCA.

Fe based (FeCSiBPCrMoAl) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The Fe-based amorphous powders and the Fe-Cu composite powders were compacted by a spark plasma sintering (SPS) process. Densification of the Fe amorphous-Cu composited powders by spark plasma sintering of was occurred through a plastic deformation of the each amorphous powder and Cu phase. The SPS samples milled by AGO-2 under 500 rpm had the best homogeneity of Cu phase and showed the smallest Cu pool size. Micro-Vickers hardness of the as-SPSed specimens was changed with the milling processes.

Fe based (FeCSiBPCrMoAl) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The experiment results show that the as-prepared Fe amorphous powders less than 90 m in size has a fully amorphous phase and its weight fraction was about 73.7%. The as-atomized amorphous Fe powders had a complete spherical shape with very clean surface. Differential scanning calorimetric results of the as-atomized Fe powders less than 90 m showed that the glass transition, T, onset crystallization, T, and super-cooled liquid range T=T-T were 512, 548 and 36, respectively. Fe amorphous powders were mixed and deformed well with 10 wt.% Cu by using AGO-2 high energy ball mill under 500 rpm.

A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the gas atomized initially and spherical powders became elongated with a maximum aspect ratio after milling for 30 h. Then, refinement and spheroidization were achieved by further milling to 70 h with a homogeneous and fine dispersion of graphite particles forming between the matrix alloy layers. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.