• Title, Summary, Keyword: High energy ball milling

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Effect of High-Energy Ball Milling on Thermoelectric Transport Properties in CoSb3 Skutterudite (고에너지 볼 밀링이 Skutterudite계 CoSb3의 열전 및 전하 전송 특성에 미치는 영향)

  • Nam, Woo Hyun;Meang, Eun-Ji;Lim, Young Soo;Lee, Soonil;Seo, Won-Seon;Lee, Jeong Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.12
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    • pp.852-856
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    • 2015
  • In this study, we investigate the effect of high-energy ball milling on thermoelectric transport properties in double-filled $CoSb_3$ skutterudite ($In_{0.2}Yb_{0.1}Co_4Sb_{12}$). $In_{0.2}Yb_{0.1}Co_4Sb_{12}$ powders are milled using high-energy ball milling for different periods of time (0, 5, 10, and 20 min), and the milled powders are consolidated into bulk samples by spark plasma sintering. Microstructure analysis shows that the high-energy ball milled bulk samples are composed of nano- and micro-grains. Because the filling fractions are reduced in the bulk samples due to the kinetic energy of the high-energy ball milling, the carrier concentration of the bulk samples decreases with the ball milling time. Furthermore, the mobility of the bulk samples also decreases with the ball milling time due to enhanced grain boundary scattering of electrons. Reduction of electrical conductivity by ball milling has a decisive effect on thermoelectric transport in the bulk samples, power factor decreases with the ball milling time.

Surface Modification of $AB_2$ Type Hydrogen Storage Alloys by Ball Milling for Ni-MH Battery (Ni-MH 전극용 $AB_2$계 수소저장합금의 볼밀링 처리에 의한 표면개질 연구)

  • Moon, Hong-Gi;Park, Choong-Nyeon;Yoo, Joung-Hyun;Park, Chan-Jin;Choi, Jeon
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.4
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    • pp.418-424
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    • 2006
  • In order to improve the activation properties of the $AB_2$ type hydrogen storage alloys for Ni-MH battery, the alloy surface was modified by employing high energy ball milling. The $Zr_{0.54}Ti_{0.45}V_{0.54}Ni_{0.87}Cr_{0.15}Co_{0.21}Mn_{0.24}$ alloy powder was ball milled for various period by using the high energy ball mill. As the ball milling time increased, activation of the $AB_2$ type composite powder electrodes were enhanced regardless of additives. When the ball milling time was small discharge capacities of the $AB_2$ type composite powder electrodes increased with the milling time. On the other hand for large milling time it decreased with increasing milling time. The maximum discharge capacity was obtained by ball milling for 3-4 min.

The Effect of Ball-milling Energy on Combustion Synthesis Coating of Cu-Al-Ni Based Intermetallics (Cu-Al-Ni계 금속간화합물의 연소합성 Coating에 미치는 Ball Mill처리의 영향)

  • Lee, Han-Young
    • Tribology and Lubricants
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    • v.27 no.1
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    • pp.1-6
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    • 2011
  • The possibility of Cu-Al-Ni intermetallic coating on the mild steel through the combustion synthesis has been investigated. In particular, the effect of the ball milling energy on the microstructure of the coating layer was examined to obtain the best coating condition. Experimental results show that Cu-Al-Ni powder compact was explosively synthesized and successfully coated with the steel matrix. It was revealed that the formation of $Cu_9Al_4$ intermetallic decreased with increase in the ball milling energy. This result supports that the high energy ball milling would be effective for obtaining the most suitable microstructure for Cu-Al-Ni coating layer. However, the excessive ball milling energy seems to decrease the bonding strength between the coating layer and the matrix.

Microstructure of W-Cu Composite Powders with Variation of Milling Method during Mechanochemical Process (기계화학적 공정의 밀링 방법에 따른 W-Cu 복합분말의 미세조직)

  • 이강원;김길수;김대건;김영도
    • Journal of Korean Powder Metallurgy Institute
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    • v.9 no.5
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    • pp.329-335
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    • 2002
  • Recently, the fabrication process of the W-Cu nanocomposite powders has been studied to improve the sinterability through the mechanical alloying and reduction of W and Cu oxide mixtures. In this study. the W-Cu composites were produced by mechanochemical process (MCP) using $WO_3-CuO$ mixtures with two different milling types of low and high energy, respectively. These ball-milled mixtures were reduced in $H_2$ atmosphere. The ball-milled and reduced powders were analyzed through XRD, SEM and TEM. The fine W-Cu powder could be obtained by the high energy ball-milling (HM) compared with the large Cu-cored structure powder by the low energy ball-milling (LM). After the HM for 20h, the W grain size of the reduced W-Cu powder was about 20-30 nm.

Effect of high energy ball milling on the structure of iron - multiwall carbon nanotubes (MWCNT) composite

  • Kumar, Akshay;Pandel, U.;Banerjee, M.K.
    • Advances in materials Research
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    • v.6 no.3
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    • pp.245-255
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    • 2017
  • High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

Spark Plasma Sintering of Stainless Steel Powders Fabricated by High Energy Ball Milling

  • Chang, Si Young;Oh, Sung-Tag;Suk, Myung-Jin;Hong, Chan Seok
    • Journal of Korean Powder Metallurgy Institute
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    • v.21 no.2
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    • pp.97-101
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    • 2014
  • The 304 stainless steel powders were prepared by high energy ball milling and subsequently sintered by spark plasma sintering, and the microstructural characteristics and micro-hardness were investigated. The initial size of the irregular shaped 304 stainless steel powders was approximately 42 ${\mu}m$. After high energy ball milling at 800 rpm for 5h, the powders became spherical with a size of approximately 2 ${\mu}m$, and without formation of reaction compounds. From TEM analysis, it was confirmed that the as-milled powders consisted of the aggregates of the nano-sized particles. As the sintering temperature increased from 1073K to 1573K, the relative density and micro-hardness of sintered sample increased. The sample sintered at 1573K showed the highest relative density of approximately 95% and a micro-hardness of 550 Hv.

Effect of Initial Silicon Scrap Size on Powder Refining Process During High Energy Ball Milling (HEBM) (폐실리콘의 고에너지 밀링 과정에서 초기 입자 크기가 분말의 미세화에 미치는 효과)

  • Song, Joon-Woo;Kim, Hyo-Seob;Kim, Sung-Shin;Koo, Jar-Myung;Hong, Soon-Jik
    • Journal of Korean Powder Metallurgy Institute
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    • v.17 no.3
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    • pp.242-250
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    • 2010
  • In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were investigated as a function of different initial powder size using the high-energy ball milling equipment, which produces the fine powder by means of an ultra high-energy within a short duration. The morphological change of the powders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasing milling time, the size of Si powder was decreased. In addition, more energy and stress for milling were required with the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball milling time. However, the refined powder started to agglomerate at 30 min milling time, while the powder size became uniform at 60 min milling time.

Synthesis of MnFeP1-xAsx Nanocrystalline Powders by High-Energy Ball Milling (고에너지볼밀링을 이용한 MnFeP1-xAsx 나노분말의 합성)

  • 조영환
    • Journal of Korean Powder Metallurgy Institute
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    • v.10 no.2
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    • pp.129-135
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    • 2003
  • Nanocrystalline powders of $MnFeP_{1-x}As_x$(x=0.45-0.6) have been synthesized by mechanochemical reaction at room temperature using high-energy ball milling from mixtures of Mn, Fe, P, and As Powders. It has been found that a mechanically induced self-propagating reaction (MSR) occurs within 2 hours of milling and it produces very fine polycrystalline powder having a hexagonal $Fe_2P$ structure. Further milling up to 24 hours did not change the crystalline and average particle sizes or the phase composition of the milling product. When x is 0.65, no reaction among the reactants has been observed even after 24 hours of milling. As the P content decreases in $MnFeP_{1-x}As_x$, the incubation time for the MSR has increased and the lattice constants in both a and c axes have changed.