• Title/Summary/Keyword: whisker

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The Synthesis of Potassium Hexatitanate Whisker by the Flux Process (융제법에 의한 육티탄산칼륨 Whisker의 합성)

  • Lee, Chul-Tae;Kim, Sung-Weon;Lee, Jin-Sik;Kim, Young-Myoung;Kwon, Kung-Taek
    • Applied Chemistry for Engineering
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    • v.5 no.3
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    • pp.478-500
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    • 1994
  • The preparation of potassium hexatitanate whisker by flux method was investigated. In this study, 8 types synthesis of flux such as $V_2O_5$, $Bi_2O_3$, $B_2O_3$, $Pb_3O_4$, KCl, $K_4P_2O_7$, $K_2WO_4$ and $K_2MoO_4$ were tested to find a suitable flux for the synthesis of potassium hexatitanate whisker. Effects of various reaction variables such as reaction temperature, time, $TiO_2$ mole ratio to $K_2CO_3$, flux mole ratio to the mixture of $K_2CO_3$ and $TiO_2$, and slow-cooling treatment on the crystallization of potassium hexatitanate whisker were investigated. $K_2MoO_4$ and $K_2WO_4$ were better flux than others tested for the synthesis of potassium hexatitanate. In the presence of $K_2MoO_4$ or $K_2WO_4$ flux, the optimum condition for the synthesis of potassium hexatitanate whisker was that reaction temperature of $1000{\sim}1100^{\circ}C$, reaction time of 5 hours, $TiO_2$ mole ratio to $K_2CO_3$ of 6.0, and flux mole ratio to mixture ($K_2O+nTiO_2$) of 4.0. Slow-cooling treatment showed good effect on the growth of long fibrous potassium hexatitanate.

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Pore Structure Modification and Characterization of Porous Alumina Filter with Chemical Vapor Infiltration (CVI) SiC Whisker (화학증착 탄화규소 휘스커에 의한 다공성 알루미나 필터의 기공구조 개질 및 특성 평가)

  • 박원순;최두진;김해두
    • Journal of the Korean Ceramic Society
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    • v.41 no.7
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    • pp.518-527
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    • 2004
  • In this study, SiC whiskers were grown in porous alumina substrate in order to enhance the filtering efficiency, performance, and durability by controlling pore morphology. This experiment was performed by Chemical Vapor Infiltration (CVI) in order to obtain the whiskers on the inside of pores as well as on the surface of porous the A1$_2$O$_3$ substrate. The deposition behavior was changed remarkably with the deposition position, temperature, and input gas ratio. First, the mean diameter of whisker was decreased as the position of observation moved into the inside of substrate due to the reactant gas depletion effect'. Second, the deposition temperature caused the changes of the deposition type such as debris, whiskers and films and the change in morphology affect the various properties. When SiC films were deposited. the gas permeability and the specific surface area decreased. However, the whisker showed the opposite result. The whiskers increase not only the specific surface area and minimizing pressure drop but also mechanical strength. Therefore it is expected that the porous alumina body which deposited the SiC whisker is the promising material for the filter trapping the particles.

Influence of Testing Method on the Fracture Toughness of Cordierite-SiC Whisker Ceramic Composites (코디어라이트-SiC위스커 복합재료에서 측정방법에 따른 파괴인성치의 변화)

  • ;Weisskopf
    • Journal of the Korean Ceramic Society
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    • v.24 no.4
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    • pp.313-320
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    • 1987
  • Fracture toughness of hot pressed cordierite-SiC whisker ceramic composites contained up to 40vol.% SiC whiskers were determined by using the indentation crack length(IC), indentation strengthin-bending(IS), and single-edge notched-beam(SENB) methods. The results were compared to stress intensity factor, KB, at the crack branching boundary measured by using the mirror zone radius (MZ) method. IS method seems to provide a more reasonable estimation of fracture toughness than other methods for these composites.

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Dependence of Harmonics Profiles on Domain Dynamics in Current-Carrying Iron Whisker

  • KIm, C.G.;Kim, D.Y.;Ryu, K.S.;Yang, Y.S.;Lee, J.G.
    • Journal of Magnetics
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    • v.1 no.2
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    • pp.60-63
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    • 1996
  • The first and second harmonics have been measured in the iron whisker with the axial current that produces a circular field. The observed harmonics profiles have been discussed in terms of theoretical analysis based on the nonlinear, asymmetric magnetization that are related to the nucleation, transformation and annihilation of domains. The change of second harmonics profile is more sensitive to the domain variation than that of first harmonics.

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Fabrication of AlN Whiskes by Self-propagating High-temperature Synthesis (자전 고온 합성법에 의한 질화 알루미늄 휘스커의 제조)

  • 이경재;장영섭;김석윤;김용석
    • Journal of the Korean Ceramic Society
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    • v.32 no.8
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    • pp.931-937
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    • 1995
  • AlN powder and whiskers were synthesized by direct nitridation of aluminum powder in pure nitrogen atmosphere. The nitridation reaction of aluminum powder was initiated by heating the sample to the ignition temperature and the reaction was finished in less than 3 minutes. AlN whisker-shaped morphology was observed predominantly when the sample was heated above 90$0^{\circ}C$.

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