• Title/Summary/Keyword: Fine powders

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Synthesis of Ultrafine and Less Agglomerated TiCN Powders by Magnesiothermic Reduction (마그네슘 열환원에 의한 저응집 초미립 TiCN 분말합성)

  • Lee, Dong-Won
    • Journal of Powder Materials
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    • v.19 no.5
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    • pp.356-361
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    • 2012
  • The ultra-fine and less agglomerated titanium carbonitride particles were successfully synthesized by magnesiothermic reduction with low feeding rate of $TiCl_4+1/4C_2Cl_4$ solution. The sub-stoichiometric titanium carbide ($TiC_{0.5{\sim}0.6}$) particles were produced by reduction of chlorine component by liquid magnesium at $800^{\circ}C$ of gaseous $TiCl_4+1/4C_2Cl_4$ and the heat treatments in vacuum were performed for 5 hours to remove the residual magnesium and magnesium chloride mixed with produced $TiC_{{\sim}0.5}$. The final $TiC_{{\sim}0.5}N_{0{\sim}0.5}$ particle with near 100 nm in mean size and high specific surface area of $65m^2/g$ was obtained by nitrification under nitrogen gas at $1,150^{\circ}C$ for 2 hrs.

Development of Tungsten Dispersed Copper Based Alloy and its Physical Property

  • Mishima, Akira;Sakaguchi, Shigeya
    • Journal of Powder Materials
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    • v.5 no.4
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    • pp.329-333
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    • 1998
  • Copper-10 wt. % tungsten alloyed powder was obtained by co-reduction of mixed tungsten-trioxide and copper oxide powders at 973 K for 7.2 Ks. In the alloy obtained by pressure-assisted sintering of this co-reduced powder, ultra fine tungsten particles (about 100nm) were dispersed uniformly in the copper matrix. At room temperature, the hardness of this alloy was Hv151 and the electrical conductivity was 85% IACS. After annealing at 1173 K for 3.6 Ks, the hardness and electrical conductivity were Hv147 and 84% IACS, respectively, and were same as before annealing. It was confirmed that the hardness and electrical conductivity of this alloy were hardly influenced by annealing condition since the microstructure of this alloy is highly stabilized.

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Characteristics of Sintering Densification of Co and Fe+Co Fine Powders (Co와 Fe+Co혼합미분의 소결치밀화 특성)

  • 임태환
    • Journal of Powder Materials
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    • v.3 no.2
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    • pp.97-103
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    • 1996
  • The densification of the compacts of pure Co, Fe+50%.Co and Fe+25% Co sintered under H$_2$ gas or in vacuum was investigated. The effects of AL, Nb, Ti, and V additions on the densification were also studied. The sintered compact of Co was fully-dense when the density of the compact was lower than $Dg^c$. However, above $Dg^{c}$, it was never fully-dense regardless of sintering atmosphere, temperature, and time. The densification of sintered compacts of Fe-50% Co and Fe-25% Co were always incomplete. While the addition of AL made all compacts fully-dense, the addition of Ti was effective for the compacts of Co and Fe-25% Co. V was effective only for the Fe-25% Co. These results tell us that the particle size of Co powder, the amount of Fe, and the amount of additives forming stable oxides play on important role for the complete densification. Therefore it is desirable to reduce or eliminate the equilibrium pressure of H$_{2}$O or CO in isolated pores to obtain a fully-dense sintered compact.

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Properties of Concrete Containing third binary mineral Admixture (3성분계 혼화재료로 사용한 콘크리트 특성)

  • 조일호;양재성;김진희
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.95-101
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    • 1999
  • This study was performed to evaluate the characteristics of workability and strength of the concrete containing mineral admixtures such as flyash, blast furnace slag, zeolite powder. As a result, considering their workability and strength, the optimum replacement ratio of them to plain concrete were obtained for each ternary admixture. This increased compressive strength was ascribed to both the closer parkinof fine particles and pozzolan reactivity of powders. This work showed that could be effectively utilized as a blending material without any decrease in the strength of early hydration stage. On the other hand, we found that the compressive strength at early ages ternary ordinary and high strength concrete untill 7 days was small, but that ternary concrete at 28days was highly increased about 31% and 15% extent.

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Preparation and Dielectric Characteristics of PTEE(Polytetrafluoroethyl one) Composites for Microwave Circuit Board (고주파용 회로기판을 위한 PTEE(Polytetrafluoroethylene) 복합체의 제조 및 유전 특성)

  • 윤기현;정도환;양병덕;장재혁;김종희
    • Journal of the Korean Ceramic Society
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    • v.40 no.8
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    • pp.735-738
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    • 2003
  • The PTFE composites for the microwave printed circuit board were prepared using woven glass fiber. The dielectric constant of the PTFE composites with oven glass fiber tended to decrease with an increase of immersion time, and was saturated at 3 times immersion. It resulted from the fact that fine powders of PTFE filled up at the pore and bend of woven glass fiber sufficiently. As the immersion time increased, the propagation velocity increased due to the reduction of dielectric constant.

Effect of Catalysts on Preparation of Mullite Precursor Using Silicic Acid Extracted by THF from Sodium Silicate (규산 나트륨으로부터 THF에 의해 추출된 규산을 이용한 Mullite 전구체 제조시 촉매에 대한 영향)

  • 정흥호;박은희;김도수;정호승;노재성
    • Journal of the Korean Ceramic Society
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    • v.37 no.6
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    • pp.517-523
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    • 2000
  • Effect of catalysts, which was catalyzed by acid(HCl and HNO3) and base(NH4OH), on characteristics of the mullite powders prepared by sol-gel methdo wa sinvestigated by XRD, TGA, SEm AND BET. As a result, weight loss as a function of catalysts was in order of HCl=32.6%>HNO3=25.44%>Non=24.0%>NH4OH=22.5%. The mullite powder dried at 100$^{\circ}C$ appeared spherical shape in acid catalyst and different shape in base catalyst, but sintering powder at 1400$^{\circ}C$ appeared very fine particle of 0.05∼0.1$\mu\textrm{m}$ regardless of catalysts. In all cae, the pore quantity, which was capable to adsoprtion, was decreased with increasing temperature. In base catalyst, no change of special surface area in mullite appeared.

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A Numerical Analysis for the Washboarding Phenomenon on the Top Surface of Fine Powders Using the Discrete Element Method (분말에서 발생하는 Washboarding 현상에 대한 이산요소법을 이용한 수치해석적 연구)

  • Lee, Seoungjun;Park, Junyoung
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.4
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    • pp.93-98
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    • 2020
  • Washboarding is a phenomenon in which a wavy shape occurs periodically and naturally on an unpaved road made of soil or gravel. This phenomenon causes high-frequency vibration of the traffic traveling on the road because of the height difference of the wave pattern, which may lead to vehicle failure. Consequently, associated research is needed concerning vehicle safety. Therefore, in this study, a numerical simulation was conducted using the discrete element method, which is often used for powder simulation. In contrast to previous studies, the results of this study demonstrate that washboarding can occur even in an environment of 1.5 m/s or less. However, the amount of washboarding is minimal. The study revealed that washboarding develops over time, such that sufficient development time is required before measurements are taken.

Material Charcterization of MR Fluids at High Frequencies (고주파 영역에서의 MR유체 특성연구)

  • Park, Kyoung-mi;Kim, Jae-hwan;Park, Seung-Bok;Kim, Kyung-Su
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.327.1-327
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    • 2002
  • MR(Magnetorheogical) fluid composed of fine iron powders dispersed in silicon oil is utilized to many smart structures and devices because of its significant rheological property change by the application of an external magnetic field. When we deal with the shock wave attenuation of warship structures, we should be able to characterize the high frequency behavior of MR fluids. So far, however, much efforts have been focused on the material characterization of MR fluids at low frequencies below 100㎐. (omitted)

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Establishments of Fabrication and Evaluation Methods for Innovative SiC Fiber Reinforced SiC Matrix Composites

  • Park, Joon-Soo;Kohyama, Akira;Hinoki, Tatsuya
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.21-24
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    • 2006
  • Based on the improvement in reinforcing SiC fibers and the utilization of very fine nano-SiC powders, the well known liquid phase sintering (LPS) process was drastically improved to become a new process called the Nano Infiltration and Transient Eutectic Phase (NITE) Process. Laboratory scale NITE-SiC/SiC composites demonstrated excellent mechanical properties, thermal conductivity, hermeticity and microstructure stability which made them attractive for not only energy application but many other industrial applications. For the real deployments of these materials, mass production system and evaluation methods, together with the design code and safety assurance systems are essential. The current efforts to establish these bases were introduced.

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A Study on Mixing for Injection Molding of Ceramic Turbo-charger Rotor for Automobile Engine. (자동차엔진용 세라믹 터보차져로터의 사출성형을 위한 혼합에 대한 연구)

  • Chang, In-C.;Ko, Jin;Yoon, Jae-R.
    • Journal of the Korean Society for Precision Engineering
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    • v.9 no.4
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    • pp.109-117
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    • 1992
  • Mixing of ceramic-binder system was investigated experimentally and theoretically for application to Ceramic Injection Molding. Polypropylene, stearic acid, and paraffin wax were selected as the binder system, and silicon nitride fine powders were selected as the ceramic material. Single screw ectruder was employed as the mixing equipment. Theoretical analysis was performed to investigate the mixedness of mixture quantitatively. The analysis predicted average residence time average total strain, and average shear stress as a function of screw speed for mixtures of different volume fraction. Qualitative mixedness of mixture and characteristics of mixing were investigated by using SEM and EPMA. In addition, rheological properties of the mixture were investigated by using a capillary rheometer to examine possibility of injection molding.

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