• Title, Summary, Keyword: $Si_3N_4$

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Nitrogenation of Coal Ash in the Presence of Carbon and Product Distributions of AlN, SiC and $Si_3N_4$ (석탄회의 탄소가 첨가된 질화반응과 AlN, SiC 그리고 $Si_3N_4$의 생성분포)

  • 양현수;홍원표;노재성;서동수;손응권
    • Journal of the Korean Ceramic Society
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    • v.27 no.8
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    • pp.965-970
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    • 1990
  • A nitrogenation of coal ash in the presence of carbon was carried out to examine the effects of reaction temperature, reaction time and carbon composition on the formation of AlN, SiC and Si3N4. Decreasing the particle size increased the formation of AlN and its maximum composition in the product was obtaiend under 1450~150$0^{\circ}C$, 2 hours of reaction time and about 30% of carbon addition(on the basis of sample weight). Compositions of SiC and Si3N4 were distributed to the opposite so that SiC showed a higher composition compared with Si3N4 at a lower temperature, a shorter reaction time and a greater carbon addition.

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High Strength $Si_3N_4/SiC$ Structural Ceramics (고강도 $Si_3N_4/SiC$ 구조세라믹스에 관한 연구)

  • 김병수;김인술;장윤식;박홍채;오기동
    • Journal of the Korean Ceramic Society
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    • v.30 no.12
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    • pp.999-1006
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    • 1993
  • Si3N4(p)-SiC(p) composites were prepared by gas pressure sintering at 190$0^{\circ}C$ for 1 hour. $\alpha$-SiC with average particle size of 0.48${\mu}{\textrm}{m}$ were dispersed from zero to 50vol% in $\alpha$-Si3N4 with average particle size of 0.5${\mu}{\textrm}{m}$. Y2O3-Al2O3 system was used as sintering aids. When 10vol% of SiC was added to Si3N4, optimum mechanical properties were observed; relative density of 98.8%, flextural strength of 930MPa, fracture toughness of 5.9MPa.m1/2 and hardness value of 1429kg/$\textrm{mm}^2$. Grain growth of $\beta$-Si3N4 was inhibited as the amount of added SiC was increased. SiC particles were found inside the $\beta$-Si3N4 intragrains in case of 10, 20 and 30vol%SiC added composites.

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$\alpha$ to $\beta$ Phase Transformation of $\alpha$-Si3N4 Whisker ($\alpha$-질화규소 Whisker의 $\alpha$/$\beta$ 상변태)

  • 박지연;김종희
    • Journal of the Korean Ceramic Society
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    • v.25 no.5
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    • pp.502-508
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    • 1988
  • The $\alpha$ to $\beta$ phase transformation of $\alpha$-Si3N4 whisker and related microstructural changes have been investigated. When only $\alpha$-Si3N4 whisker was heat treated in the range 1650~175$0^{\circ}C$, the $\alpha$ to $\beta$ phase transformation occured. In this case, it eas suggested that the oxygen content in $\alpha$-Si3N4 whisker affected the transformation behavior. Although $\alpha$-Si3N4 whisker with Si was heat treated under the same condition, however, the variation of $\beta$- fraction had a similar tendency with heat treating time. Therfore, it was considered that the oxygen content in $\alpha$-Si3N4 whisker affected the transformation behavior dominently rather than the content of added Si. The added $\beta$ phase did not affect the transformation behaviro of $\alpha$-Si3N4 whisker.

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Fabrication and characterization of Copper/Silicon Nitride composites

  • Ahmed, Mahmoud A.;Daoush, Walid M.;El-Nikhaily, Ahmed E.
    • Advances in materials Research
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    • v.5 no.3
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    • pp.131-140
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    • 2016
  • Copper/silicon nitride ($Cu/Si_3N_4$) composites are fabricated by powder technology process. Copper is used as metal matrix and very fine $Si_3N_4$ particles (less than 1 micron) as reinforcement material. The investigated powder were used to prepare homogenous ($Cu/Si_3N_4$) composite mixtures with different $Si_3N_4$ weight percentage (2, 4, 6, 8 and10). The produced mixtures were cold pressed and sintered at different temperatures (850, 950, 1000, $1050^{\circ}C$). The microstructure and the chemical composition of the produced $Cu/Si_3N_4$ composites were investigated by (SEM) and XRD. It was observed that the $Si_3N_4$ particles were homogeneously distributed in the Cu matrix. The density, electrical conductivity and coefficient of thermal expansion of the produced $Cu/Si_3N_4$ composites were measured. The relative green density, sintered density, electrical conductivity as well as coefficient of thermal expansion were decreased by increasing the reinforcement phase ($Si_3N_4$) content in the copper matrix. It is also founded that the sintered density and electrical conductivity of the $Cu/Si_3N_4$ composites were increased by increase the sintering temperature.

Effect of Si/α-Si3N4 Ratio on the Shape of Silicon Nitride Particles Produced by SHS Method

  • Kim, Min-Sung;Park, Dong-Soo;Han, Byung-Dong;Kim, Hai-Doo;Park, Chan
    • Journal of the Korean Ceramic Society
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    • v.39 no.3
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    • pp.217-221
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    • 2002
  • Si and ${\alpha}-Si_3N_4$ powder mixtures added with 3 wt% $Y_2O_3$ were reacted under 5 MPa nitrogen pressure. The reaction products contained ${\alpha}-Si_3N_4$ particles with elongated shapes. Length and width of the elongated grains were the maximum when the starting powder mixture of 50 wt% Si - 47 wt% ${\alpha}-Si_3N_4$ and 3 wt% $Y_2O_3$ was used. Aspect ratio of the elongated grains were between 4.4 and 5. When the starting powder mixture contained 70 wt% Si, large particles with irregular shapes appeared. Meanwhile, the reaction did not proceed when the starting powder mixture contained 30 wt% Si and less. The SHS product was easy to crush and the elongated particles obtained from the starting powder mixtures of 40 wt% Si - 57 wt% ${\alpha}-Si_3N_4$ - 3 wt% $Y_2O_3$ and 50 wt% Si - 47 wt% ${\alpha}-Si_3N_4$ - 3 wt% $Y_2O_3$ were good candidates for the seeds.

Microstructure and Mechanical Properties of Self-Reinforced Si3N4 Ceramic Prepared by Pressureless-Sintering (상압소결에 의해 제조한 자체 강인화 질화규소 세리믹의 미세조직과 기계적 성질)

  • 김완중;이영규;조원승;최상욱
    • Journal of the Korean Ceramic Society
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    • v.36 no.5
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    • pp.547-554
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    • 1999
  • The self-reinforced Si3N4 ceramics were prepared by pressureless-sintering using ${\beta}$-Si3N4 whiskers as a seed. Effects of ${\beta}$-Si3N4 whiskers on microstructure and mechanical properties and the ${\alpha}$ to ${\beta}$ phase transition of Si3N4 were investigated. The self-reinforced Si3N4 ceramics were densified(relative density$\geq$98%) by pressureless-sintering (1800$^{\circ}C$ 2h) using 8mol% Y2O3 and 6mol% Al2O3 as sintering aids and 5 vol% ${\beta}$-Si3N4 whiskers within self-reinforced Si3N4 ceramic seemed to hinder the densification owing to their acicular shapes but accelerated the ${\alpha}$ to ${\beta}$ phase transition because they acted as pre-existing nuclei. It was found that the more ${\beta}$-Si3N4 nucei the faster ${\alpha}$ to ${\beta}$ phase transition.

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Effect of $Si_3N_4$ Addition on the Microstructure and PTCR Characteristics in Semiconducting $BaTiO_3$ Ceramics (반도성 $BaTiO_3$ 세라믹스의 미세구조 및 PTCR 특성에 미치는 $Si_3N_4$ 첨가효과)

  • 김준수;정윤해;이병하
    • Journal of the Korean Ceramic Society
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    • v.31 no.10
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    • pp.1089-1098
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    • 1994
  • The effect of Si3N4 addition on the microstructure and PTCR characteristics of BaTiO3 was studied. When 0.1 mol% Sb2O3-doped BaTiO3 codoped with Si3N4 (0.1, 0.25, 0.5, 0.75, and 1 wt%, respectively) were sintered, their microstructures were changed by the amount of the liquid phase as a result of eutectic reaction at 126$0^{\circ}C$. By these microstructural changes, the specific resistivity ratio($\rho$max/$\rho$min) with Si3N4 content variation of 0.1 mol% Sb2O3-doped BaTiO3 ceramics sintered at 130$0^{\circ}C$ for 1 hour varied between 3.70$\times$102(0.1 wt% Si3N4) to 1.16$\times$103 (1wt% Si3N4).

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Preparation of β-SiAlON Powder by Combustion Reaction in the System of Si-Al-SiO2-NH4F(β-Si3N4) (Si-Al-SiO2-NH4F(β-Si3N4)계에서 연소반응에 의한 β-SiAlON분말의 제조)

  • Min, Hyun-Hong;Shin, Chang-Yun;Won, Chang-Whan
    • Journal of the Korean Ceramic Society
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    • v.43 no.10
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    • pp.595-600
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    • 2006
  • The preparation of $\beta$-SiAlON powder by SHS in the system of $Si-Al-SiO_2-NH_4F(\beta-Si_3N_4)$ was investigated in this study. In the preparation of SiAlON powder, the effect of gas pressure, compositions such as Si, $NH_4F$, \beta-Si_3N_4$ and additive in mixture on the reactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure $\beta$-SiAlON was $3Si+Al+2SiO_2+NH_4F$. The $\beta$-SiAlON powder synthesized in this condition was a single phase $\beta$-SiAlON with a rod like morphology.

Microstructures Of Continuously Porous SiC-Si3N4 Composites Fabricated Using Waste SiC Sludge (폐 SiC 슬러지를 이용하여 제조한 연속다공질 SiC-Si3N4 복합체의 미세조직)

  • Gain Asit Kumar;Lee Hee-Jung;Jang Hee-Dong;Lee Byong-Taek
    • Korean Journal of Materials Research
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    • v.15 no.3
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    • pp.177-182
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    • 2005
  • Large amounts of the waste SiC sludge containing small amounts of Si and organic lubricant were produced during the wire cutting process of the single silicon crystal ingots. The waste SiC sludge was purified by the washing process and the purified SiC powders were used to fabricate continuously porous $SiC-Si_3N_4$ composites using a fibrous monolithic process, in which carbon, $6wt\%\;Y_2O_3-2\;wt\%\;A1_2O_3$ and ethylene vinyl acetate were added as a pore-forming agent, sintering additives, and binder, respectively. In the burning-out process, carbon was fully removed and continuously porous $SiC-Si_3N_4$ composites were successfully fabricated. The green bodies containing SiC, Si particles and sintering additives were nitrided at $1410^{\circ}C$ in a flowing $N_2+10\%\;H_2$ gas mixture. Continuously porous composites were combined with SiC, ${\alpha}Si_3N_4,\;\beta-Si_3N_4$ and a few $\%$ of Fe phases. The pore size of the 2nd and the 3rd passed $SiC-Si_3N_4$ composites was $260\;{\mu}m$ and $35\;{\mu}m$ in diameter, respectively.

Fabrication of in-situ Formed Namo-Composite Using Polymer Precursor : I. Adsorption Behavior of Polymer Followed $SiO_2$ Surface formation onto Silicon Nitride Surface (폴리머 Precursor를 이용한 in-situ 나노 복합체의 제조 : I. 질화규소 표면에서의 $SiO_2$ 피막형성에 따른 폴리머의 흡착거동)

  • 정연길;백운규
    • Journal of the Korean Ceramic Society
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    • v.37 no.3
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    • pp.280-287
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    • 2000
  • Adsorption behavior and amount of phenolic resin followed silica (SiO2) formation onto silicon nitride(Si3N4) surface were investigated using electrokinetic sonic amplitude (ESA) technique and with UV spectrometer, to fabricate Si3N4/SiC nano-composite based on reaction between SiO2 formed and phenolic resin absorbed onto Si3N4 particle. The amount of SiO2 formed and carbon from phenolic resin absorbed onto Si3N4 surface were calculated quantitatively to adjust the reaction between SiO2 and phenolic resin, resulting in no residual SiO2 and carbon. As a result, pre-heated tempeature for optimized reaction was below 25$0^{\circ}C$, in which there was no residual SiO2 and carbon.

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