• Title/Summary/Keyword: Si-C-N Precursor powder

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Synthesis and Characterization of Si-C-N Precursor by Using Chemical Vapor Condensation Method (화학기상응축법을 이용한 Si-C-N Precursor 분말의 합성 및 특성평가)

  • Kim, Hyoung-In;Kim, Dae-Jung;Hong, Jin-Seok;So, Myoung-Gi
    • Journal of the Korean Ceramic Society
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    • v.39 no.8
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    • pp.783-788
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    • 2002
  • In this study, nano-sized Si-C-N precursor powders were synthesized by Chemical Vapor Condensation Method(CVC) using TMS(Tetramethylsilane: Si($CH_3)_4$), $NH_3$ and $H_2$ gases under the various reaction conditions of the reaction temperature, TMS/$NH_3$ ratio and TMS/$H_2$ ratio. XRD and FESEM were used to analysis the crystalline phase and the average particle size of the synthesized powders. It was found that the obtained powders under the considering conditions were all spherical amorphous powder with the particle size of 87∼130 nm. The particle size was decreased as the reaction temperature increased and TMS/$NH_3$ and TMS/$H_2$ ratio decreased. As the results of EA analysis, it was found that the synthesized powders had been formed the powders composed of Si, N, C and H. Through FT-IR results, it was found that the synthesized powders were Si-C-N precursor powders with Si-C, Si-N and C-N bonds.

Synthesis of Silicon Carbide Nano-Powder from a Silicon-Organic Precursor by RF Inductive Thermal Plasma (RF 유도 열플라즈마를 이용한 유기 용매로 부터의 탄화규소 나노 분말 합성)

  • Ko, Sang-Min;Koo, Sang-Man;Kim, Jin-Ho;Cho, Woo-Seok;Hwang, Kwang-Taek
    • Journal of the Korean Ceramic Society
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    • v.49 no.6
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    • pp.523-527
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    • 2012
  • Silicon carbide (SiC) has recently drawn an enormous amount of industrial interest due to its useful mechanical properties, such as its thermal resistance, abrasion resistance and thermal conductivity at high temperatures. In this study, RF thermal plasma (PL-35 Induction Plasma, Tekna CO., Canada) was utilized for the synthesis of high-purity SiC powder from an organic precursor (hexamethyldisilazane, vinyltrimethoxysilane). It was found that the SiC powders obtained by the RF thermal plasma treatment included free carbon and amorphous silica ($SiO_2$). The SiC powders were further purified by a thermal treatment and a HF treatment, resulting in high-purity SiC nano-powder. The particle diameter of the synthesized SiC powder was less than 30 nm. Detailed properties of the microstructure, phase composition, and free carbon content were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), a thermogravimetric (TG) analysis, according to the and Brunauer-Emmett-Teller (BET) specific surface area from N2 isotherms at 77 K.

Magnetic Properties of Co-substituted Ba-ferrite Powder by Sol-gel Method (졸-겔법에 의한 Cobalt 치환된 Ba-ferrite 분말의 자기적 특성)

  • Choi, Hyun-Seung;Park, Hyo-Yul;Yoon, Seog-Young;Shin, Hak-Gi;Kim, Tae-Ok
    • Journal of the Korean Ceramic Society
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    • v.39 no.8
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    • pp.789-794
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    • 2002
  • In this study, nano-sized Si-C-N precursor powders were synthesized by Chemical Vapor Condensation Method(CVC) using TMS(Tetramethylsilane: $Si(CH_3)_4$), $NH_3$ and $H_2$ gases under the various reaction conditions of the reaction temperature, TMS/$NH_3$ ratio and TMS/$H_2$ ratio. XRD and FESEM were used to analysis the crystalline phase and the average particle size of the synthesized powders. It was found that the obtained powders under the considering conditions were all spherical amorphous powder with the particle size of 87∼130 nm. The particle size was decreased as the reaction temperature increased and TMS/$NH_3$ and TMS/$H_2$ ratio decreased. As the results of EA analysis, it was found that the synthesized powders had been formed the powders composed of Si, N, C and H. Through FT-IR results, it was found that the synthesized powders were Si-C-N precursor powders with Si-C, Si-N and C-N bonds.

Reaction Bonded Si3N4 from Si-Polysilazane Mixture (규소 고분자 복합체를 이용한 반응소결 질화규소)

  • Hong, Sung-Jin;Ahn, Hyo-Chang;Kim, Deug-Joong
    • Journal of the Korean Ceramic Society
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    • v.47 no.6
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    • pp.572-577
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    • 2010
  • Reaction-bonded $Si_3N_4$ has cost-reduction merit because inexpensive silicon powder was used as a start material. But its density was not so high enough to be used for structural materials. So the sintered reaction-bonded $Si_3N_4$techniques were developed to solve the low density problem. In this study the sintered reaction-bonded $Si_3N_4$ manufacturing method by using polymer precursor which recently attained significant interest owing to the good shaping and processing ability was proposed. The formations, properties of reaction-bonded $Si_3N_4$ from silicon and polysilazane mixture were investigated. High density reaction-bonded $Si_3N_4$ was manufactured from silicon and silicon-containing preceramic polymers and post-sintering technique. The mixtures of silicon powder and polysilazane were prepared and reaction sintered in $N_2$ atmosphere at $1350^{\circ}C$ and post-sintered at 1600~$1950^{\circ}C$. Density and phase were analyzed and correlated to the resulting material properties.

NANO-SIZED COMPOSITE MATERIALS WITH HIGH PERFORMANCE

  • Niihara, N.;Choa, H.Y.;Sekino, T.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 1996.11a
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    • pp.6-6
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    • 1996
  • Ceramic based nanocomposite, in which nano-sized ceramics and metals were dispersed within matrix grains and/or at grain boundaries, were successfully fabricated in the ceramic/cerarnic and ceramic/metal composite systems such as $Al_2O_3$/SiC, $Al_2O_3$/$Si_3N_4$, MgO/SiC, mullite/SiC, $Si_3N_4/SiC, $Si_3N_4$/B, $Al_2O_3$/W, $Al_2O_3$/Mo, $Al_2O_3$/Ni and $ZrO_2$/Mo systems. In these systems, the ceramiclceramic composites were fabricated from homogeneously mixed powders, powders with thin coatings of the second phases and amorphous precursor composite powders by usual powder metallurgical methods. The ceramiclmetal nanocomposites were prepared by combination of H2 reduction of metal oxides in the early stage of sinterings and usual powder metallurgical processes. The transmission electron microscopic observation for the $Al_2O_3$/SiC nanocomposite indicated that the second phases less than 70nm were mainly located within matrix grains and the larger particles were dispersed at the grain boundaries. The similar observation was also identified for other cerarnic/ceramic and ceramiclmetal nanocornposites. The striking findings in these nanocomposites were that mechanical properties were significantly improved by the nano-sized dispersion from 5 to 10 vol% even at high temperatures. For example, the improvement in hcture strength by 2 to 5 times and in creep resistance by 2 to 4 orders was observed not only for the ceramidceramic nanocomposites but also for the ceramiclmetal nanocomposites with only 5~01%se cond phase. The newly developed silicon nitride/boron nitride nanocomposites, in which nano-sized hexagonal BN particulates with low Young's modulus and fracture strength were dispersed mainly within matrix grains, gave also the strong improvement in fracture strength and thermal shock fracture resistance. In presentation, the process-rnicro/nanostructure-properties relationship will be presented in detail. The special emphasis will be placed on the understanding of the roles of nano-sized dispersions on mechanical properties.

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A preparation of hexacelsian powder by solution-polymerization route and its phase transformation behavior (Solution- polymerization 방법에 의한 hexacelsian 분말의 합성 및 상전이 공정에 의한 celsian 소결체의 제조)

  • Sang-Jin Lee;Young-Soo Yoon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.3
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    • pp.428-436
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    • 1997
  • Hexacelsian ($BaO{\cdot}Al_2O_3{\cdot}2SiO_2$) powder was prepared by a solution-polymerization route employing PVA solution as a polymeric carrier. A fine amorphous-type hexacelsian powder with an average particle size of 0.8 $\mu \textrm{m}$ and a BET specific surface area of $63 \textrm{m}^2$/g was made by a ball-milling the powder precursor for 12 h after calcination at $800^{\circ}C$ for :1 h. A densified hexacelsian was obtained through sintering at $1550^{\circ}C$ for 2 h under an air atmosphere. The $\alpha\longleftrightarrow\beta$ and $\beta\longleftrightarrow\gamma$ displacive phase transformation in polycrystalline hexacelsia,n was examined by using dilatometry and differential scanning calorimtry. The reconstructive transformation between hexacelsian and celsian was obtained by annealing at $1600^{\circ}C$ for 72h. Volume contraction of 5.6% was accompanied by the reconstructive transformation.

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Synthesis Characteristics of ZnO Powder from Precursors Composed of Nitrate-Citrate Compounds (Nitrate-Citrate 혼합 전구체로부터 ZnO 입자의 합성반응 특성)

  • Yang, Si Woo;Lee, Seung Ho;Lim, Dae Ho;Yoo, Dong Jun;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.54 no.3
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    • pp.299-304
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    • 2016
  • Characteristics of self-propagating reaction for the preparation of ZnO powder from precursors composed of nitrate and citrate compounds were examined. The ratio of C/N was maintained in range of 0.7~0.8 to initiate the self-propagating reaction between the reducing citrate and oxidizing nitrate groups. The samples were decomposed thermally by using TGA. The sudden decomposition occurred in the range of X > 0.5 in a very short time with a very sharp decrease of mass, indicating that the self-propagating reaction would occur. Friedman, Ozawa-Flynn-Wall and Vyazovkin methods were employed to predict the activation energy, reaction order and frequency factor of the reaction rate in the rate determining step of X < 0.5 range. The activation energy increased with increasing fractional conversion in the range of 46~130 (kJ/min). The reaction order decreased in the range of 2.9~0.9, while the frequency factor increased in the range of 85~278 ($min^{-1}$), respectively, with increasing the rate of temperature increase.