• Corrosion Science and Technology
• /
• v.21 no.6
• /
• pp.445-453
• /
• 2022

SiO_x was prepared from a mixture of Si and SiO₂ via high-energy ball milling as a negative electrode material for Li-ion batteries. The molar ratio of Si to SiO₂ as precursors and the milling time were varied to identify the synthetic condition that could exhibit desirable anode performances. With an appropriate milling time, the material showed a unique microstructure in which amorphous Si nanoparticles were intimately embedded within the SiO₂ matrix. The interface between the Si and SiO₂ was composed of silicon suboxides with Si oxidation states from 0 to +4 as proven by X-ray photoelectron spectroscopy and electrochemical analysis. With the addition of a conductive carbon (Super P carbon black) as a coating material, the SiO_x/C manifested superior specific capacity to a commercial SiO_x/C composite without compromising its cycle-life performance. The simple mechanochemical method described in this study will shed light on cost-effective synthesis of high-capacity silicon oxides as promising anode materials.

• Journal of Powder Materials
• /
• v.17 no.2
• /
• pp.130-135
• /
• 2010

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 $110\;{\mu}m$. After milling for 5 h, the shape of powders changed to round shape and their mean powder size was approximately $5\;{\mu}m$, 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 $7\;{\mu}m$ 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.

• Journal of Powder Materials
• /
• v.29 no.5
• /
• pp.376-381
• /
• 2022

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 high-performance WS₂-based photodiodes and transistors used in practical semiconductor applications.

• Journal of the Korean Ceramic Society
• /
• v.43 no.9 s.292
• /
• pp.519-526
• /
• 2006

A full-factorial design of experiments with three input factors and two levels for each factor including center points was utilized for the preparation and characterization of twelve types of $BaTiO_3$ slips for tape casting. Ceramic powders with different particle sizes, different milling methods such as high energy milling and conventional ball milling, and two types of dispersant with different polymeric species were chosen as input factors in order to investigate their effects on slip and on green tape properties. Tape casting, a small rectangular-shaped K-square preparation, characterization and quantitative data analysis using statistical software were followed. Ceramic powder was the most significant among three input factors for the output responses of slip viscosity and green tape density, showing more favorable results with large particles than with very fine ones. In addition, high energy milling for only 30 min was more efficient than 24h of conventional ball milling in terms of powder dispersion and milling. The optimum condition based on the experimental results was a slip exposed to high energy milling with large ceramic particles along with a methylethyl acetate dispersant.

• Korean Journal of Materials Research
• /
• v.31 no.1
• /
• pp.23-28
• /
• 2021

The purpose of this study is to prepare WO3 nanopowders by high-energy milling in mixture gas (7 % H2+Ar) with various milling times (10, 30, and 60 min). The phase transformation, particle size and light absorption properties of WO3 nanopowders during reduction via high-energy milling are studied. It is found that the particle size of the WO3 decreases from about 30 ㎛ to 20 nm, and the grain size of WO3 decreases rapidly with increasing milling time. Furthermore, the surface of the particles due to the pulverization process is observed to change to an amorphous structure. UV/Vis spectrophotometry shows that WO3 powder with increasing milling times (10, 30, 60 min) effectively extends the light absorption properties to the visible region. WO3 powder changes from yellow to gray and can be seen as a phenomenon in which the progress of the color changes to blue. The characterization of WO3 is performed by high resolution X-ray diffractometry, Field emission scanning electron microscopy, Transmission electron microscopy, UV/Vis spectrophotometry and Particle size analysis.

• Journal of Powder Materials
• /
• v.29 no.1
• /
• pp.34-40
• /
• 2022

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 1,600℃.

• Journal of Powder Materials
• /
• v.18 no.4
• /
• pp.378-384
• /
• 2011

In this research, the indium dissolution properties of the waste LCD panel powders were investigated as a function of milling time fabricated by high-energy ball milling (HEBM) process. The particle morphology of waste LCD panel powders changed from sharp and irregular shape of initial cullet to spherical shape with an increase in milling time. The particle size quickly decreased to 15 ${\mu}m$ until the first minute, then decreased gradually about 6 ${\mu}m$ with presence of agglomerated particles after 5 minutes, which increased gradually reaching a uniform size of 13 ${\mu}m$ consist of agglomerated particles after 30 minutes. The glass recovery, after dissolution, was over 99% at initial cullet, which decreased to 90.1 and 78.6% with increasing milling time of 1 and 30 minute respectively, due to a loss in remaining powder of the surface ball and jar, as well as the filter paper. The dissolution amount of indium out of the initial cullet was 208 ppm before milling, turning into 223 ppm for the mechanically milled powder after 1 minute, and nearly 146~125 ppm with further increase in milling time because of the reaction surface decrease of powders due to agglomeration. With this process, maximum dissolving indium amount (223 ppm) could be achieved at a particle size of 15 ${\mu}m$ with 1 minute of milling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.1
• /
• pp.39-45
• /
• 2004

Fine LaAlO$_3$ powders wore successfully synthesized from La$_2$O$_3$ and ${\gamma}$ $Al_2$O$_3$ powders milling for 10∼50 hours via the high energy milling technique (mechanochemical method) in room temperature and air. The particle size of LaAlO$_3$ powder were estimated from XRD patterns and SEM images to be 160∼180 nm. The LaAlO$_3$ ceramics arc derived for the synthesized powders (milling for 10, 30 and 50 hours) by sintering at 140$0^{\circ}C$ and 150$0^{\circ}C$. The micrographs of grains showed an agglomeration and the degree of agglomeration increased with the milling time. The LaAlO$_3$ made from synthesized powders milling for 50 hours can be sintered to 99.5％ of theoretical density at 150$0^{\circ}C$ for 1 hour. These ceramics exhibits a dielectric constant of 20, a dielectric loss of 0.0003 and a temperature coefficient of capacitance of 15 ppm/$^{\circ}C$ at 1 MHz.

• Journal of the Korean Ceramic Society
• /
• v.45 no.6
• /
• pp.363-367
• /
• 2008

Lead-free $(K_{0.44}Na_{0.52})(Nb_{0.86}Ta_{0.10})-0.04LiSbO_3$ 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 ($k_p$) and piezoelectric constant ($d_{33}$) of a specimen sintered at $1050^{\circ}C$ are 0.44 and 267 pC/N, respectively.

• Korean Journal of Materials Research
• /
• v.31 no.12
• /
• pp.677-681
• /
• 2021

The Mn-Zn ferrite powders were prepared by high energy ball milling, then compacted and sintered at various temperatures to assess their sintering behavior and magnetic properties. The initial ferrite powders were spherical in shape with the size of approximately 70 ㎛. After 3 h of ball milling at 300 rpm, aggregated powders ~230 nm in size and composed of ~15 nm nanoparticles were formed. The milled powders had a density of ~70 % when compacted at 490 MPa for 3 min. In the samples subsequently sintered at 1,273 K ~ 1,673 K for 3 h, the MnZnFe₂O₄ phase was detected. The density of the sintered samples had a tendency to increase with increasing sintering temperature up to 1,473 K, which produced the highest density of 98 %. On the other hand, the sample sintered at 1,373 K had the highest micro-hardness of approximately 610 Hv, which is due to much finer grains.