• Title/Summary/Keyword: High-energy milling

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The effect of nano-sized starting materials and excess amount of Bi on the dielectric/piezoelectric properties of 0.94[(BixNa0.5)TiO3]-0.06[BaTiO3] lead free piezoelectric ceramics

  • Khansur, Neamul Hayet;Ur, Soon-Chul;Yoon, Man-Soon
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2009.11a
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    • pp.31.1-31.1
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    • 2009
  • In an approach to acclimate ourselves torecent ecological consciousness trend, a lead-free piezoelectric material, bismuth sodium titanate (abbreviated as BNT) based bismuth sodium barium titanate (abbreviated as BNT-BT), was considered as an environment-friendly alternative for a lead based piezoelectric system. Ceramic specimens of0.94[(BixNa0.5)TiO3]-0.06[BaTiO3] (x = 0.500~0.515) compositions were prepared by a modified mixed oxide method. To increase the chemical homogeneity andre action activity, high energy mechanical milling machine and pre-milled nanosized powder has been used. In this method (BixNa0.5)TiO3 (x=0.500~0.515) andBaTiO3 were prepared separately from pre-milled constituent materials at low calcination temperature and then separately prepared BNTX (X=1, 2, 3 and 4) and BT were mixed by high energy mechanical milling machine. Without further calcination step the mixed powders were pressed into disk shape and sintered at $1110^{\circ}C$. Microstructures, phase structures and electrical properties of the ceramic specimens were systematically investigated. Highly dense ceramic specimens with homogenous grains were prepared in spite of relatively low sintering temperature. Phase structures were not significantly influenced by the excess amount Bi. Large variation on the piezoelectric and dielectric properties was detected at relative high excess Bi amounts. When $x{\leq}0.505$, the specimens exhibit insignificant variation in piezoelectric and dielectric constant though depolarization temperature is found to be decreased. Considerable amount of decrease in piezoelectric and dielectric properties are observed with higher excess of Bi amounts ($x{\geq}0.505$). This research indicates the advantages of high energy mechanical milling and importance of proper maintenance of Bi stoichiometry.

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Synthesis of Carbonyl Iron-reinforced Polystyrene by High Energy Ball Milling

  • Nguyen, Hong-Hai;Nguyen, Minh-Thuyet;Kim, Won Joo;Kim, Jin-Chun;Kim, Young-Soo;Kim, Young-Hyuk;Nazarenko, Olga B.
    • Journal of Powder Materials
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    • v.23 no.4
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    • pp.276-281
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    • 2016
  • Carbonyl iron (CI) is successfully incorporated as an additive into a polystyrene (PS) matrix via a highenergy ball milling method, under an n-hexane medium with volume fractions between 1% and 5% for electromagnetic interference shielding applications by the combination of magnetic CI and an insulating PS matrix. The morphology and the dispersion of CI are investigated by field emission scanning electron microscopy, which indicates a uniform distribution of CI in the PS matrix after 2 h of milling. The thermal behavior results indicate no significant degradation of the PS when there is a slight increase in the onset temperature with the addition of CI powder, when compared to the as-received PS pellet. After milling, there are no interactions between the CI and the PS matrix, as confirmed by Fourier transformed infrared spectroscopy. In this study, the milled CI-PS powder is extruded to make filaments, and can have potential applications in the 3-D printing industry.

Effect of Co-Substitution on the Crystallization and Magnetic Properties of a Mechanically Milled Nd15(Fe1-xCox)77B8 (x=0-0.6) Alloy

  • Kwon, H.W.;Yang, C.J.
    • Journal of Magnetics
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    • v.7 no.4
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    • pp.143-146
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    • 2002
  • Mechanical milling technique is considered to be a useful way of processing the fine Nd-Fe-B-type powder with high coercivity. In the present study, phase evolution of the $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ (x=0-0.6) alloys during the high energy mechanical milling and annealing was investigated. The effect of Co-substitution on the crystallization of the mechanically milled $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ amorphous material was examined. The Nd-Fe-B-type alloys can be amorphized completely by a high-energy mechanical milling. On annealing of the amorphous material, fine $\alpha$-Fe crystallites form first from the amorphous. These fine $\alpha$-Fe crystallites reacts with the remaining amorphous afterwards, leading to crystallization to $Nd_2Fe_{14}$B phase. The Co-substitution for Fe in $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ ($\mu$x=0∼0.6) alloys lower significantly the crystallization temperature of the amorphous phase to the $Nd_2Fe_{14}$B phase. The mechanically milled and annealed $Nd_{15}Fe_{77}B_8$ alloy without Co-substitution exhibits consistently better magnetic properties with respect to the alloys with Co-substitution.

Characteristics of WO3-CuO Powder Mixture Prepared by High-Energy Ball Milling in a Bead Mill for the Synthesis of W-Cu Nanocomposite Powder (W-Cu 나노분말 합성을 위해 비드밀에서 고에너지 볼밀링 공정에 의해 제조된 WO3-CuO 혼합분말의 특성 연구)

  • Park, Hae-Ryong;Ryu, Sung-Soo
    • Journal of Powder Materials
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    • v.24 no.5
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    • pp.406-413
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    • 2017
  • A Nanosized $WO_3$ 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 $WO_3-CuO$ powder mixtures is investigated. The results show that the ball-milled $WO_3-CuO$ 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 $37m^2/g$, and powder mean particle size ($D_{50}$) of $0.57{\mu}m$. The $WO_3-CuO$ powder mixtures milled for 10 h are heat-treated at different temperatures in $H_2$ atmosphere to produce W-Cu powder. The XRD results shows that both the $WO_3$ and CuO phases can be reduced to W and Cu phases at temperatures over $700^{\circ}C$. 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.

Effect of High Energy Ball Milling on Sintering Behavior and Thermal Conductivity of Direct Nitrided AlN Powder (직접질화법 AlN 분말의 소결거동 및 열전도도에 미치는 고에너지 볼밀링 효과)

  • Park, Hae-Ryong;Kim, Hyung-Tae;Lee, Sung-Min;Kim, Young-Do;Ryu, Sung-Soo
    • Journal of the Korean Ceramic Society
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    • v.48 no.5
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    • pp.418-425
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    • 2011
  • In this study, a high energy ball milling process was introduced in order to improve the densification of direct nitrided AlN powder. The sintering behavior and thermal conductivity of the AlN milled powder was investigated. The mixture of AlN powder and 5 wt% $Y_2O_3$ as a sintering additive was pulverized and dispersed by a bead mill with very small $ZrO_2$ bead media. The milled powders were sintered at $1700^{\circ}C-1800^{\circ}C$ for 4 h under $N_2$ atmosphere. The results showed that the sintered density was enhanced with increasing milling time due to the particle refinement as well as the increase in oxygen contents. Appropriate milling time was effective for the improvement of thermal conductivity, but the extensive millied powder formed more fractions of secondary phase during sintering, resulted in the decrease in thermal conductivity. The AlN powder milled for 10min after sintering at $1800^{\circ}C$ revealed the highest thermal conductivity, of 164W/$m{\cdot}K$ in tne densified AlN sintered at $1800^{\circ}C$.

Fabrication of Ultra Fine β-phase Ti-Nb-Sn-HA Composite by Pulse Current Activated Sintering

  • Woo, Kee-Do;Wang, Xiaopeng;Kang, Duck-Soo;Kim, Sang-Hyuk;Woo, Jeong-Nam;Park, Sang-Hoon;Liuc, Zhiguang
    • Journal of Powder Materials
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    • v.17 no.6
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    • pp.443-448
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    • 2010
  • The $\beta$ phase Ti-Nb-Sn-HA bio materials were successfully fabricated by high energy mechanical milling and pulse current activated sintering (PCAS). Ti-6Al-4V ELI alloy has been widely used as biomaterial. But the Al has been inducing Alzheimer disease and V is classified as toxic element. In this study, ultra fine sized Ti-Nb-Sn-HA powder was produced by high energy mechanical milling machine. The $\beta$ phase Ti-Nb-Sn-HA powders were obtained after 12hr milling from $\alpha$ phase. And ultra fine grain sized Ti-Nb-Sn-HA composites could be fabricated using PCAS without grain growth. After sintering, the microstructures and phase-transformation of Ti-Nb-Sn-HA biomaterials were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The relative density was obtained by Archimedes principle and the hardness was measured by Vickers hardness tester. The $\beta$-Ti phase was obtained after 12h milling. As result of hardness and relative density, 12h milled Ti-Nb-Sn-HA composite has the highest values.

Densification and Microstructure of Ultrafine-sized AlN Powder Prepared by a High Energy Ball Milling Process (고에너지 볼밀링 방법에 의해 얻어진 초미립 AlN 분말의 치밀화 및 미세구조)

  • Park, Hae-Ryong;Kim, Young-Do;Ryu, Sung-Soo
    • Journal of Powder Materials
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    • v.19 no.1
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    • pp.25-31
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    • 2012
  • 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.% $Y_2O_3$ as a sintering additive was pulverized and dispersed up to 50 min in a bead mill with very small $ZrO_2$ beads. Ultrafine AlN powder with a particle size of 600 nm and a specific surface area of 9.54 $m^2/g$ was prepared after milling for 50 min. The milled powders were pressureless-sintered at $1700^{\circ}C-1800^{\circ}C$ for 4 h under $N_2$ atmosphere. This powder showed excellent sinterability leading to full densification after sintering at $1700^{\circ}C$ 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 $ZrO_2$ impurity.

An Investigation of the Stability of Y2O3 and Sintering Behavior of Fe-Based ODS Particles Prepared by High Energy Ball Milling

  • Park, Eun-Kwang;Hong, Sung-Mo;Park, Jin-Ju;Lee, Min-Ku;Rhee, Chang-Kyu;Seol, Kyeong-Won
    • Journal of Powder Materials
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    • v.20 no.4
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    • pp.275-279
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    • 2013
  • Fe-based oxide dispersion strengthened (ODS) powders were produced by high energy ball milling, followed by spark plasma sintering (SPS) for consolidation. The mixed powders of 84Fe-14Cr-$2Y_2O_3$ (wt%) were mechanically milled for 10 and 90 mins, and then consolidated at different temperatures ($900{\sim}1100^{\circ}C$). Mechanically-Alloyed (MAed) particles were examined by means of cross-sectional images using scanning electron microscopy (SEM). Both mechanical alloying and sintering behavior was investigated by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). To confirm the thermal behavior of $Y_2O_3$, a replica method was applied after the SPS process. From the SEM observation, MAed powders milled for 10 min showed a lamella structure consisting of rich regions of Fe and Cr, while both regions were fully alloyed after 90 min. The results of sintering behavior clearly indicate that as the SPS temperature increased, micro-sized defects decreased and the density of consolidated ODS alloys increased. TEM images revealed that precipitates smaller than 50 nm consisted of $YCrO_3$.

Enhancement in Piezoelectric Properties of PZT-Based Ceramics by High Energy Ball-Milling Treatment of Solid-State Synthesized Powders

  • Kim, Dae-Uk;Lee, Han-Bok;Hung, Nguyen Viet;Pham, Ky Nam;Han, Hyoung-Su;Lee, Jae-Shin
    • Journal of Powder Materials
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    • v.17 no.5
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    • pp.404-408
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    • 2010
  • The effects of high energy ball-milling (HEBM) on the sintering behavior and piezoelectric properties of 0.1 wt% $Li_2CO_3$ doped 0.8Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-0.2Pb($Zr_{0.475}Ti_{0.525}$)$O_3$ (PMN-PZT) ceramics were investigated. It was found that HEBM treatment was quite effective to reduce the average particle size down to 300 nm, leading to increased density as well as enhanced piezoelectric properties of a sintered specimen even though prolonged HEBM resulted in unwanted secondary phases that caused a degradation of piezoelectric properties. The dielectric constant ($\varepsilon_r$), piezoelectric coupling factor ($k_p$) and piezoelectric constant $d_{33}$ of 0.1 wt% $Li_2CO_3$ doped PMN-PZT ceramics prepared via HEBM for 10 h reached 2040, 0.68 and 554 pC/N, respectively.

Effect of Grain Size on Nanostructured Fe-20 wt.%Si Alloy Powders Produced by High-energy ball milling (고에너지 볼밀링으로 제조된 나노구조 Fe-20 wt.%Si 합금 분말의 자성 특성에 미치는 결정립 크기의 영향)

  • Kim, Se-Hoon;Lee, Young Jung;Lee, Baek-Hee;Lee, Kyu Hwan;Kim, Young Do
    • Journal of Powder Materials
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    • v.12 no.5 s.52
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    • pp.362-368
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    • 2005
  • The structural and magnetic properties of nanostructued Fe-20 ;wt.%Si alloy powders were investigated. Commercial Fe-20 wt.%Si alloy powders (Hoeganaes Co., USA) with 99.9% purities were used to fabricate the nanostructure Fe-Si alloy powders through a high-energy ball milling process. The alloy powders were fabricated at 400 rpm for 50 h, resulting in an average grain size of 16 nm. The nanostructured powder was characterized by fcc $Fe_{3}Si$ and hcp $Fe_{5}Si_3$ phases and exhibited a minimum coercivity of approximately 50 Oe.