• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.154-154
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• 2008

Although the screen printing technology using photosensitive carbon nanotube (CNT) paste has many advantages such as low cost, simple process, uniform emission, and capability of mass production, the CNT paste needs to be improved further in CNT dispersion, printability, adhesion, electrical conductivity, population of CNT emitters, etc. Ball milling has been frequently employed to prepare the CNT paste as ball milling can mix its ingredients very well and easily cut the long, entangled CNTs. This study carried out a parametric approach to fabricating the CNT paste in terms of low-energy ball milling and a paste composition. Field emission properties of the CNT paste was characterized with CNT dispersion and electrical conductivity which were measured by a UV-Vis spectrophotometer and a 4-point probe method, respectively. Main variables in formulating the CNT paste include a length of milling time, and amounts of CNTs and conductive inorganic fillers. In particular, we varied not only the contents of conductive fillers but also used two different sizes of filler particles of ${\mu}m$ and nm ranges. Among many variations of conductive fillers, the best field emission characteristics occurred at the 5 wt% fillers with the mixing ratio of 3:1 for ${\mu}m$-and nm-sizes. The amount and size of fillers has a great effect on the morphology, processing stability, and field emission characteristics of CNT emitter dots. The addition a small amount of nm-size fillers considerably improved the field emission characteristics of the photosensitive CNT paste.

• Carbon letters
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• v.26
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• pp.11-17
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• 2018

Milled carbon fiber (mCF) was prepared by a ball milling process, and X-ray diffraction (XRD) diffractograms were obtained by a $2{\theta}$ continuous scanning analysis to study mCF crystallinity as a function of milling time. The raw material for the mCF was polyacrylonitrile-based carbon fiber (T700). As the milling time increased, the mean particle size of the mCF consistently decreased, reaching $1.826{\mu}m$ at a milling time of 18 h. The XRD analysis showed that, as the milling time increased, the fraction of the crystalline carbon decreased, while the fraction of the amorphous carbon increased. The (002) peak became asymmetric before and after milling as the left side of the peak showed an increasingly gentle slope. For analysis, the asymmetric (002) peak was deconvoluted into two peaks, less-developed crystalline carbon (LDCC) and more-developed crystalline carbon. In both peaks, Lc decreased and $d_{002}$ increased, but no significant change was observed after 6 h of milling time. In addition, the fraction of LDCC increased. As the milling continued, the mCF became more amorphous, possibly due to damage to the crystal lattices by the milling.

• Journal of the Korean Magnetics Society
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• v.9 no.4
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• pp.217-222
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• 1999

The pick up impurity was studied for preparing the NiCuZn ferrite powder by a ball milling method that usually uses in the industrial ceramic process. The raw materials of NiO, CuO, ZnO, and $Fe_2O_3$ powder were weighted according to various spinel composition and mixed for 18 hrs by a wet ball milling method after that the slurry was followed by spray dried and calcined at $700^{\circ}C$ 3 hrs. The calcined NCZF powder was finally ball milled during 65 hrs as same method. The stainless steel ball and jar are used as mixing and milling equipment and the solid concentration of the slurry was 25 vol%. The impurities, stainless steel pickup, were effected by the composition of raw materials especially iron oxide, nickel oxide in the mixing process and by the rate of calcine of NiCuZn ferrite in final milling process. The empirical equation of stainless steel pickup was driven in the wet ball milling system. Finally, the composition of NiCuZn ferrite could be controlled by the empirical equation.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.133-137
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• 2014

As a preceding process for preparing several micrometer sized Ag-coated Cu flakes, ball milling of submicrometer-sized Cu particles synthesized through a wet chemical method was performed in order to convert the particles into flakes. To suppress oxidation and aggregation of the particles during ball milling, ethylene glycol and ethyl acetate were used as a medium and a surface modifying agent, respectively. Results obtained with different rotation speeds of a jar indicated that the rotation speed changes a rotating mode, and strikingly alters the final shapes and shape uniformity of Cu particles after milling. The diameter of zirconia ball was also confirmed. Although there was aggregates in the initial submicrometer-sized Cu particles, therefore, well-dispersed Cu flakes with a size of several micrometers were successfully prepared by ball milling through optimization of rotation speed, amount of ethyl acetate, and diameter of zirconia ball.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.245-252
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• 1993

We investigated the changes of (U, Ce)$O_2$ powder characteristics with $CeO_2$ contents and ball-milling time and then studied on the sintering properties with those (U, Ce)$O_2$ powder characteristics. From the results of this study, it was concluded that the longer ball-milling time of (U, Ce)$O_2$ powder was, the finer its particle size was. Green and sintered densities were decreased with $CeO_2$ contensts increase. And also $CeO_2$ was recongized deteriorating oxide on the $UO_2$ sintering. In case of the lOwt. % $CeO_2$ contents, (U, Ce)$O_2$ sintered pellet which was made of ball-milled powder for 4 hours had few pores and its pores got near to the sphere. And its sintered density had the highest. Because its powder had higher surface area and its packing ratio was appropriated much better than others.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.53-61
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• 2015

High-energy ball milling was tested as a method for producing Ultra High Molecular Weight Polyethylene (UHMWPE)- based nanodielectrics containing 1 wt% and 5 wt% OctaIsoButylPOSS (OibPOSS). Qualitative and quantitative evaluations were used to explore the compatibility between OibPOSS and PE. Several ball milling variables were optimized in a bid to achieve UHMWPE/OibPOSS nanodielectrics. The morphology, as well as the thermal and the dielectric properties of the samples, were characterized by scanning electron microscopy, thermogravimetric analysis, broadband dielectric spectroscopy, and progressive-stress breakdown tests. The results showed that (i) ball milling was an effective method for producing UHMWPE/OibPOSS dielectric composites, but appeared ineffective in dispersing OibPOSS at the nanoscale, and (ii) the resulting UHMWPE/OibPOSS dielectric composites presented thermal and dielectric properties similar to those of neat UHMWPE.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.726-734
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• 1995

Pb(Zr0.53Ti0.47)O3 (PZT) ceramics having different microstructures were fabricated at low temperatures using calcined PZT powders with addition of excess PbO powder and/or ball milling. The effects of excess PbO and ball milling time on the microstructure, the sintering characteristic, and the mechanical properties of these ceramics were studied. Fine powders with average particle size of 0.38㎛ could be obtained by ball milling with 2.5 mm Ф zirconia balls for 120 hours. By the addition of 2mol% of excess PbO to these powders, it was possible to obtain well-densitified PZT ceramics at low sintering temperature of 980℃. Densification behavior of PZT was affected by the addition of excess PbO powder, while, grain growth was hardly affected by PbO addition. It was observed that Vicker's hardness decreased and fracture toughness increased with the increasing amount of PbO. At 1mol% excess PbO, it was shown that the minimum values of hardness and maximum fracture toughness were achieved. In addition, with increasing sintering time, the fracture toughness decreased and the hardness increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.338-338
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• 2007

$LiFePO_4-C$ cathode materials were prepared by hydrothermal reaction and ball-milling. In order to enhance the electronic conductivity of $LiFePO_4$, 10% of acetylene black was added. During the ball-milling, different revolutions per minute (100, 200 and 300 rpm) was carried out. The structural and morphological performance of $LiFePO_4-C$ powders were characterized by X-ray diffraction and scanning electron microscope. The X-ray diffraction results demonstrated that $LiFePO_4-C$ powders had an orthorhombic olivine-type structure with a space group of Pnma. $LiFePO_4-C$ batteries were characterized electrochemically by charge/discharge experiments. The charge/discharge experiments indicated that $LiFePO_4-C$/Li batteries by 300 rpm of the ball-milling exhibited the best electrochemical performance with the discharge capacity of 126mAh/g at a discharge rate of $0.1mA/cm^2$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.143-146
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• 1995

Due to the recent growth of die/mold machining industry, demands for the high-precision and the high0quality of die product are increasing rapidly. Free surfaces of die/mold are often manufactured using the ball-end milling process. It is difficult to find the cutting condition of the ball-end milling process due to the free form machining for the various tool paths on inclined surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1003-1008
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• 1997

In this paper, the prediction of cutting force and tool deflection in the ball-end milling process are studied. Identifying various cutting region using Z-map, cutting force in the ball-end milling process can be predicted. Cutting force deflects the tool and the tool deflection changes the cutting force. Tool deflection is included in the cutting force prediction. Tool deflecition also causes machining error of the machined surface. A series of experiments were performed to verify the simulated cutting force and machining error.