Heekyu Choi

In this paper, a comparison of cellulose nanofiber (CNF) fabrication from Gelidium amansii using two kinds of grinding processes is presented. The cellulose from Gelidium amansii is pretreated with hydrogen peroxide and sodium carbonate in a separating and bleaching process. Then, two grinding processes (method A and B) are used to fabricate CNFs. The first is a traditional method of fabricating CNFs using a disc grinder, whereas the second method is identical to the first, but includes an additional step involving a planetary ball mill. In the new method (method B), dry cellulose powder is prepared using a planetary ball mill, which has the advantage of long-term storage and maintains the original quality of the cellulose. The morphological changes of the dry cellulose powder and CNFs are determined using scanning electron microscopy and field emission scanning electron microscopy. The physical characteristics of the CNFs are found to be significantly different when we change the disc grinder used in the grinding method to produce nanometer scale where the best result is homogeneous, uniform CNFs with a fabricated width of 19 nm.

This study investigated the effect of three different ball materials on the metal-based carbon nanotube (CNT) composites used as surface coatings on metal-powder to fabricate high-quality nanocomposites. The effect of ball material, different rotation speeds, and milling times on the coating characteristics of the metal-based nanocomposite were studied. The mechanical dry coating was used to fabricate CNT coatings on the surface of copper powder particles via two different ball milling machines such as a traditional ball mill and a stirred ball mill. We explored the effect of the milling media of the ball mill under different ball materials and ball sizes on the metal powder during the ball milling process with DEM simulation. Using discrete element method simulation to obtain the average velocity, force, and, kinetic energy of the milling media in a low and high energy ball mills.

Carbon nanotubes (CNTs) have received interest as an attractive reinforcing agent metal matrix composites regarded as an increase to mechanical properties of the final product. Aluminum/carbon nanotubes (Al/CNTs) nanocomposites were observed with different raw material at the optimized experimental condition. In this study, Al-based CNTs composites were three different samples, including un-milled Al, un-milled Al with CNTs, and milled Al with CNTs nanocomposites in the presence of additional CNTs with various experimental conditions while using a traditional ball mill (TBM). The particle morphology and CNT dispersions of milled composites were respectively analysed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM), and the mechanical properties of the fabricated composites were tested. In each sample, CNTs were well dispersed on the surface of Al powder at different experimental conditions for milling in a TBM. The Al/CNTs nanocomposites were processed by compacting, sintering and rolling process. The Vickers hardness was used to characterize the mechanical properties. The hardness of Al/CNTs nanocomposites that were fabricated with milled Al with CNT was higher than the reached to in the nanocomposites prepared with the use of un-milled Al with CNT nanocomposites. Therefore, the discrete element method (DEM) simulation was used to complete quantitative analysis. The flow pattern, impact force, and energy at various experimental conditions are considered. The results of the simulations are compared with experimental data.

An experimental investigation has been conducted on grinding of copper powders using different ball-milling machines. A various parameters including rotation speed and grinding time and ball sizes are used to change the particle morphology of the copper powders. The effects of the ball mill operation condition on the morphology of Cu powders in the dry-type milling process using three different types of ball mill: traditional ball mill (TBM), stirred ball mill (SBM), and planetary ball mill (PBM). A new evaluation method, which can provide relatively accurate results, is used to analyze and compare the grinding performance of three different ball millings. The experimental results suggest that the particle size and morphology of copper particle can easily be controlled by changing grinding conditions of these ball millings. The results were systematically analyzed using scanning electron microscopy (SEM) and particle size analyzer (PSA).

Wet ultra fine grinding of a calcite powder has been investigated in a stirred ball mill with respect to the effect of slurry concentration. The grinding rate on the submicrometer range was measured and the grinding constant on the grinding rate ( K ) in the grinding kinetics equation was examined. It is observed that the grinding rate for calcite in the submicrometer size range is different for different sample concentrations. It was found that the lower the sample concentration, the better the grinding rate. Furthermore, an empirical grinding rate ( K )‐sample concentration model provides a good fit to the grinding results under the experimental conditions investigated. The K improved by a maximum of 1.6 times at 700 rpm and 19.1 times 300 rpm for various sample concentrations, respectively. We confirmed that sample concentration affected the grinding rate of the submicrometer‐size powder during the grinding process.