• Title, Summary, Keyword: Carbothermal reduction

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A Study on the Synthesis of Alkoxides and Sialon (알콕사이드와 사이알론 합성에 관한 연구)

  • Ho Ha;Heecheol Lee
    • Journal of the Korean Chemical Society
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    • v.32 no.3
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    • pp.267-275
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    • 1988
  • Fine powders of amorphous $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$ system were prepared by hydrolysis of solutions containing alkoxides, aluminium tri-isopropoxide and silicon tetra-ethoxide. High purity ultrafine ${\beta}-sialon$ powders were prepared by the carbothermal reduction-nitridation of amorphous $Al_2O_3-SiO_2$ powders mixed with carbon black as a reducing agent. In the hydrolysis step the effect of the factors such as pH, reaction temperature and amount of water on the conversion rate of alkoxides to oxides was investigated. In the carbothermal reduction-nitridation the reaction path was assumed by the analysis of intermediates formed in the process of ${\beta}-sialon$ synthesis and the reaction kinetics of ${\beta}-sialon$ formation was considered.

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Synthesis of $\beta$다-Sialon with Various Compositions from Kaolin (카올린으로부터 조성이 다른$\beta$다-Sialon의 합성)

  • 최상욱;서규식;이종진
    • Journal of the Korean Ceramic Society
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    • v.23 no.5
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    • pp.17-24
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    • 1986
  • β'-Sialon with different compositions was synthesized by the carbothermal reduction-nitridation of compacts containing kaolin graphite and silicon or aluminum at temperature of 1300-1450℃ under flowing gas of 90% N2-10% H2 or 20hrs. Quantitative analysis of minerals which were formed in the specimens was carried out by using the calibration curve which has been prepared from X-ray diffraction patterns. The obtained results were as follows : 1. In the formation of β'-Sialon by carbothermal reduction-nutridation of Si-Al-O-C system mixtures at 1400℃ for 20hrs. (2) β'-Sialon as a major mineral and α-Al2O3 as a minor mineral were identified in the specimen which was prepared of kaolin and graphite. (3)α-Al2O3 and 15R as a minor minerals were measured in the specimen which was prepared of kaolin aluminum and graphite. (4) AlN instead of α-Al2O3 and 15R was formed in the compacts that excess graphite(=35 wt%) was added to the mixture of kaolin and aluminium. 2. As the reaction time and temperature were increased the formation of β'-Sialon was increased whereas the phases of mllite SiC and Si2ON2 were decreased gradually.

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Synthesis of SiC Whiskers from Rice Hulls (생왕겨를 이용한 실리콘 카바이드 합성)

  • 길경선;김종학;고인용
    • Journal of the Korean Institute of Resources Recycling
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    • v.2 no.4
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    • pp.17-22
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    • 1993
  • SiC whiskers were synthesized from rice hulls and activated carbon by carbothermal reduction method. The effects of gases and various additives were studied. Carbothermal reduction to produce SiC whiskers was conducted at $1450^{\circ}C$ and the synthesized SiC whiskers were examined using SEM and XRD. The length of whiskers is increased with the increases of $H_2$concentration and total gas flows. The most favorable form of SiC whiskers couble be obtained in the following experimental conditins : Ar : $H_2$=300:45(ml/min), $SiO_2$(inrice hulls): $CaF_2$=1:0.5:0.5(mole ratio) and the addition of Ni flakes ($1{\times}1$mm).

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Synthesis and Characterization of Fiberous AlN by Electrospinning (전기방사에 의한 섬유상 질화알루미늄 합성 및 특성 평가)

  • Chun, Seung-Yeop;Hwang, Jin-Ah;Chu, Jae-Uk;Chun, Myoung-Pyo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.7
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    • pp.441-446
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    • 2017
  • Aluminum nitride fibers were synthesized by carbothermal reduction and nitridation of precursor fibers obtained by electrospinning. The starting materials used to synthesize the AlN fibers were $Al(NO_3)_3{\cdot}9H_2O$ and urea. Polyvinylpyrrolidone with increasing viscidity was used as the carbon source to obtain a composite solution. The mixed solution was drawn into a plastic syringe with a stainless steel needle, which was used as the spinneret and connected to a 20 kV power supply. A high voltage was supplied to the solution to facilitate the formation of a dense net of fibers on the collector. The precursor fibers were dried at $100^{\circ}C$ and then heated to $1,400^{\circ}C$ for 1 h in a microwave furnace under $N_2$ gas flow for the carbothermal reduction and nitridation. X-ray diffraction studies indicated that the synthesized fibers consisted of the AlN phase. Field emission scanning electron microscopy studies indicated that the diameter of the calcined fibers was approximately 100 nm.