• Title/Summary/Keyword: powder synthesis

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Preparation of WC Powders by SHS Process in the Presence of Alkali Salts (자전연소합성법에서의 알칼리염을 이용한 WC 분말의 제조)

  • Won, Hyung-Il;Nersisyan, Hayk;Won, Chang-Whan
    • Journal of the Korean Ceramic Society
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    • v.44 no.3 s.298
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    • pp.152-156
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    • 2007
  • Tungsten carbide powder was synthesized by SHS (self-propagating high-temperature synthesis). Except $WO_{3}$, each concentration of raw material ($WO_{3},\;Mg,\;NaCl,\;Na_{2}CO_{3},\;C$) was investigated. Final product was characterized by XRD and SEM. X-ray data demonstrated that the $NaCl+Na_{2}CO_{3}$ combined mixture has superiority in the WC formation process. Single phase and submicrometer WC powder was synthesized at the temperature below $1600^{\circ}C$. The role of sodium salts in combustion process was discussed, and chemical mechanism of WC formation was proposed. WC powder prepared by salt-assisted combustion synthesis has a size $0.2{\sim}3\;{\mu}m$ and low agglomeration degree.

The Synthesis of $BaTiO_3$ using continuous process in a bubble column reactor (기포탑반응기에서 연속공정을 이용한 $BaTiO_3$ 분말의 제조)

  • 현성호;김정환;허윤행
    • Journal of environmental and Sanitary engineering
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    • v.11 no.1
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    • pp.63-70
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    • 1996
  • The synthesis of high purity and ultra-fine $BaTiO_3$ by precipitation with gaseous $NH_3$ as precipitator was investigated to find an alternative process to solve various problems of recent wet methods. A synthesis process for $BaTiO_3$ powder using $NH_3$ gas as a precipitator in a bubble column reactor was experimentally successful in developing the production process of piezoelectric ceramic $BaTiO_3$ powder. And a 2.33m1/sec is approprite for the feed flow rate, $BaTiO_3$ powder produced under above the condition is spherical type, its particle size was about $0.2{\mu}m$.

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Synthesis of Carbon Nanotubes by Chemical Method at Warm Temperatures (탄소나노튜브의 중저온에서의 화학적 합성)

  • Ahn, Jung-Ho;Lee, Sang-Hyun;Kim, Yong-Jin;Chung, Byung-Sik
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.305-312
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    • 2006
  • Amorphous carbon nanotubes were synthesized by a reaction of benzene, ferrocene and Na mixture in a small autoclave at temperatures as low as $400^{\circ}C$. The resulting carbon nanotubes were short and straight, but their inner hole was filled with residual products. The addition of quartz to the reacting mixture considerably promoted the formation of carbon nanotubes. A careful examination of powder structure suggested that the nanotubes in this process were mainly formed by surface diffusion of carbon atoms at the surface of solid catalytic particles, not by VLS(vapor-liquid-solid) mechanism.

Pore Structure and Mechanic:11 Property of Porous TiNi Biomaterial Produced by Self-Propagating High-Temperature Synthesis (고온자전합성법으로 제조된 다공성 TiNi 생체재료의 기공구조 및 기계적 특성)

  • 김지순;강지훈;양석균;정순호;권영순
    • Journal of Powder Materials
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    • v.10 no.1
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    • pp.34-39
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    • 2003
  • Porous TiNi bodies were produced by Self-propagating High-temperature Synthesis (SHS) method from a powder mixture of Ti and Ni. Porosity, pore size and structure, mechanical property, and transformation temperature of TiNi product were investigated. The average porosity and pore size of produced porous TiNi body are 63% and $216\mutextrm{m}$, respectively. XRD analysis showed that the major phase of produced TiNi body is B2 phase. Its average fracture strength and elastic modulus measured under dry condition were $22\pm2$ MPa and $0.18\pm0.01$GPa, respectively. It could be strained up to 7.3 %. The transformation temperatures determined by DSC showed the $M_s$ temperature of $67^{\circ}C$ and $A_f$ temperature of $99^{\circ}C$.

The Sialon Synthesis from Natural Silica and Al Powder Mixture by Using Home-style Microwave Oven (가정용 전자렌지를 사용한 천연규석분말과 Al분말 성형체로부터 사이알론상 합성에 관한 연구)

  • 안주삼
    • Journal of the Korean Ceramic Society
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    • v.34 no.1
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    • pp.1-6
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    • 1997
  • In home-style microwave oven, silica-Al powder mixture was ignited among pellets and combustion wave-front propagated to produce Si+AIN+Al2O3 as resultant phases under N2 atmosphere. Without cooling pro-cedure the resultant phases of Si+AIN+Al2O3 continously absorbed microwave and were heated to be syn-thesized into sialon phases. This synthesis rate of sialon phases from silica-Al powder mixture in home-style microwave oven was higher than that in conventional furnace, and total processing time was around 1 hour, which could save energy and cost.

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Study on Self-Propagating High-Temperature Synthesis of TiN Powder (SHS 공정에 의한 TiN 분말합성에 관한 연구)

  • ;S.G. Vadchenco
    • Journal of the Korean Ceramic Society
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    • v.33 no.1
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    • pp.41-48
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    • 1996
  • Self-propagating High-temperature Synthesis of Ti+N system has been investigated using the cylindrical high pressure reactor. The nitrogen pressure was varied from 40 to 80 atmosphere and TiNx(x=0.55) powder produced by SHS process was used as a diluent in order to control the reaction. Both the velocity of surface reaction and the ratio of TiN synthesis increased with increasing the nitrogen pressure. As the amount of diluent increases the degree of conversion to titanium nitride increases. Homogenious TiN powder was obtained in the composition 50Ti+50TiN0.94(diluent)

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Electrical and Optical Properties of PLZT Ceramics Prepared by Flux Method (용융염 합성법에 의한 PLZT 세라믹스의 제작과 그 전기적.광학적 특성)

  • 남효덕
    • Journal of the Korean Ceramic Society
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    • v.23 no.4
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    • pp.62-68
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    • 1986
  • $(Pb_{1-x} La_x)(Zr_{0.65} Ti_{0.35})_{1-x/4}O_3$ (PLZT X/65/35) powders were prepared by molten salt synthesis using NaCl-K Cl and conventional calcining of oxides. The effects of molten salt on formation and charactrization of PLZT powder and on dielectric piezolectric and optical properties of PLZT ceramics were studied, The completed PLZT powder formation in the presence of fused salt was attained at 50-10$0^{\circ}C$ lower temperature than that in solid state reaction and the particle size of the powder made by molten salt synthesis was markedly increased with increasing calcining temperature. The substitution of Na and/or K ions in NaCl-KCl for Pb ion in process of molten salt synthesis was increased with increasing La concentration Z. These substituted Na and/or K ions were identified as the origins of decreasing coupl-ing factor and optical transmittance of PLZT ceramics.

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Properties and Shape Control of YAG Powder Prepared by Hydrothermal Reaction (수열반응 조건에 의한 YAG 분말의 특성과 형상제어)

  • 지성훈;김상문;구자인;김태옥
    • Journal of the Korean Ceramic Society
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    • v.37 no.8
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    • pp.739-744
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    • 2000
  • YAG(Y3Al5O12) as host material of YAG:Tb3+ was studied via hydrothermal synthesis of metal hydroxides. We changed the kind of mineralizer, the concentrations and process conditions in hydrothermal synthesis. As a result, we found, acicular YAG powders were obtained by the use of KOH as a mineralizer, the concentration of KOH affected the shape and size of YAG powder. Fine grained YAG were perpared by the use of NH4OH as a mineralizer and the concentration of NH4OH affected crystal phases but did not affect particle size. We could finally get the spherical looking YAG powder at 8 M NH4OH and at 35$0^{\circ}C$ for 12h. The average particle size was about 0.2${\mu}{\textrm}{m}$.

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