• Title, Summary, Keyword: $Si_3N_4$

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Effect of Si3N4 Buffer Layer on Transmittance of TiO2/Si3N4/Ag/Si3N4/TiO2 Multi Layered Structure (TiO2/Si3N4/Ag/Si3N4/TiO2 다층구조에서 Si3N4 버퍼층이 투과율에 미치는 영향)

  • Lee, Seo-Hee;Jang, Gun-Eik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.1
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    • pp.44-47
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    • 2012
  • The $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ multi layered structure was designed for the possible application of transparent electrodes in PDP (Plasma Display Panel). Multi layered film was deposited on a glass substrate at room temperature by DC/RF magnetron sputtering system and EMP (Essential Macleod Program) was adopted to optimize the optical characteristics of film. During the deposition process, the Ag layer in $TiO_2/Ag/TiO_2$ became heavily oxidized and the filter characteristic was degraded easily. In thus study, Si3N4 layer was used as a diffusion buffer layer between $TiO_2$ and Ag. in order to prevent the oxidation of Ag layer in $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ structure. It was confirmed that $Si_3N_4$ layer is one of candidate materials acting as diffusin barrier between $TiO_2/Ag/TiO_2$.

Fabrication of $Si_3N_4-SiC$ Nanocomposites by Hot Pressing (Hot Pressing에 의한 $Si_3N_4-SiC$ 나노복합체의 제조)

  • 김성현;김인술;박홍채;오기동
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.1021-1029
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    • 1994
  • SiC ultrafine particles of 1, 10, 20 and 30 vol% were dispersed in $\alpha$-Si3N4 matrix and hot-pressed under the condition of 30 MPa at 1800 and 190$0^{\circ}C$ respectively. Physical, mechanical properties and microstructures of sintered Si3N4-SiC nanocomposites were investigated. Flexural strength and density of Si3N4-10 vol% SiC nanocomposites hot-pressed at 190$0^{\circ}C$ represented the 1002 MPa and 97.9%T.D respectively, and it was confirmed as a remarkable improvement of 67% compared to Si3N4 monolith. Fracture toughness was shown as 7.2 MPa.m1/2 when the same composition was hot pressed at 180$0^{\circ}C$. This effect was supposed to be due to the improvement of microstructure by the adequate suppression of the excessive growth of Si3N4 grain with SiC nano-particles.

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Syntheses of SiC and $SiC-Si_3N_4$ Powder from Jecheon Quartz (제천규석으로부터 SiC 및 $SiC-Si_3N_4$계 분말 합성)

  • 이홍림;배철훈;문준화
    • Journal of the Korean Ceramic Society
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    • v.23 no.1
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    • pp.67-73
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    • 1986
  • SiC and $SiC-Si_3N_4$ powder were synthesized via the carbiding and carbiding-nitriding reaction of Jecheon quartz respectively using graphite as a reducing agent. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbiding-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $H_2$ atmosphere. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbidint-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $N_2-H_2$ atmosphere. The ratio of $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ content in a produced composite could be controlled by adjusting the reaction time and gaseous mixture.

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In-Situ Synthesis of $\textrm{Si}_{3}\textrm{N}_{4}$-AIN Ceramic Composites ($\textrm{Si}_{3}\textrm{N}_{4}$-AIN 복합세라믹스의 In-Situ합성)

  • Lee, Byeong-Taek;Kim, Hae-Du;Heo, Seok-Hwan;Lee, Chan-Gyu
    • Korean Journal of Materials Research
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    • v.8 no.1
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    • pp.27-32
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    • 1998
  • In-Sit반응소결에의해 Si과 AI금속분말을 이용하여 Si$_{3}$N$_{4}$-AIN 복합세라믹스를 합성하였다. 합성된 Si$_{3}$N$_{4}$-AIN복합세라믹스의 미세조직과 결정구조를 해석하기 위해, OM, TEM, XRD및 EDX를 이용하였으며, Si$_{3}$N$_{4}$-AIN -20wt.%AIN복합세라믹스에서 Si의 질화율은 97%로 가장 높았다. Si$_{3}$N$_{4}$-AIN 복합세라믹스에서 Si의 질화율은 AI첨가량 증가에 따라 감소하였다. 대부분의 AI입자들은 다결정 AI입자들은 다결정 AIN(4-H구조)로 완전질화되었으며, 따라서 잔류 AI상은 반응소결체내에서 관찰되지 않았다. Si$_{3}$N$_{4}$의 결정구조는 $\alpha$$\beta$구조가 혼재된 상태이며, 잔류 Si입자내에서는 미소균열 및 전위가 관찰되었다. AI/Si$_{3}$N$_{4}$와 Si$_{3}$N$_{4}$ 두계면에서 이들은 거친 형상을 보이지만, 계면반응상은 관찰되지 않았다.

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Cutting characteristic of SiC-$Si_3N_4$ ceramic cutting tools (SiC-$Si_3N_4$계 세라믹 절삭공구의 절삭특성 평가)

  • 박준석;김경재;권원태;김영욱
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.898-901
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    • 2000
  • It is known that Si3N4 ceramic insert has less hardness than Al2O3 ceramic insert. But Si3N4 ceramic insert has not only high toughness and strength but also low thermal expansion coefficient, which makes it has longer tool life under thermal stress condition. In this study, commercial Si3N4 ceramic insert and home-made SiC-Si3N4 ceramic insert which has different sintering time and chemical composition is tested under various cutting conditions. The experimental result is compared in terms of tool life and cutting force. Generally, As the cutting speed and the feed rate increased, the cutting force and the flank wear increased too. The performance of SiC-Si3N4 ceramic insert shows the possibility to be a new ceramic tool.

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Cutting characteristics of in situ toughened $SiC-Si_3N_4$ composite (현장인화 $SiC-Si_3N_4$ 복합재료의 절삭성능 평가)

  • 김경재;박준석;권원태;김영욱
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.386-391
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    • 2000
  • It is known that Si$_3$N$_4$ceramic insert has less hardness than A1$_2$O$_3$ceramic insert. But Si$_3$N$_4$ceramic insert has not only high toughness and strength but also low thermal expansion coefficient, which makes it has longer tool life under thermal stress condition. In this study, commercial Si$_3$N$_4$ ceramic insert and home-made SiC-Si$_3$N$_4$ceramic insert which has different sintering time and chemical composition is tested under various cutting conditions. The experimental result is compared in terms of tool life and cutting force. Generally, As the cutting speed and the feed rate increased, the cutting force and the flank wear increased too. The performance of SiC-Si$_3$N$_4$ceramic insert shows the possibility to be a new ceramic tool.

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Mechanical Properties and Microstructures of Self-toughened Silicon Nitride Cermic Prepared by Microstructural Control (미세구조 제어에 의해 제조한 자체 강인화 질화규소 세라믹의 기계적 성질과 미세조직)

  • 김완중;이영규;조원승;최상욱
    • Journal of the Korean Ceramic Society
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    • v.36 no.4
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    • pp.432-443
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    • 1999
  • The self-toughened Si3N4 ceramics where needle-like coarse ${\beta}$-Si3N4 grains were dispersed within fine-grain-ed matrix were prepared via hot-prssing at 1730$^{\circ}C$ for 2 h using 5 vol% ${\beta}$-Si3N4 whiskers as a seed. In this study the microstructures and mechanical properties of self-toughened Si3N4 ceramics were investigated. The flexural strength of self-toughened Si3N4 ceramics was increased from 600-800 MPa of the Si3N4 monolith to 830-1025 MPa. The KIC was also increased from 4.0-5.0MPa$.$m1/2 of the Si3N4 monolith to 5.8-6.5MPa$.$m1/2$.$The needle-like coarse Si3N4 grains in self-toughened ceramics were considered to induce various toughening mechanisms including the crack deflection pull-out and bridging and to contribute to KIC improvement. In ad-dition to toughening mechanisms the KIC improvement was considered to be partially indebted also to the orien-tation of large ${\beta}$-Si3N4 grains and to the promoting effect of ${\beta}$-Si3N4 whiskers on the ${\alpha}$ to ${\beta}$ transtion.

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Photovoltaic Effects of the p$\cdot$Si-Electrolyte Junction (p$\cdot$Si-전해질 접합의 광기전력 효과)

  • Han, Seok-Yong;Kim, Yeon-Hui;Kim, Hwa-Taek
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.19 no.6
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    • pp.52-54
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    • 1982
  • p·Si-전해질 접합을 전해질로 6N H2SO4, 6N H2SO4(Ti3+), 6N H2SO4(Ti4+), 6N H2SO4(Ti4+/Ti3+)을 사용하여 만들었다. 이들 전해질중 6N H2SO4(Ti4-/Ti3+)을 사용할 때 p·Si 광음극이 안정하게 동학하며 높은 광전 감도를 가지고 있었다. p·Si-electrolyte junction are prepared by using p·Si photocatode in four different electrolytes such as 6N H2SO4, 6N H2SO4(Ti3+), 6N H2SO4(Ti4+), 6N H2SO4(Ti4+/Ti3+) respectively. Among those electrolytes 6N H2SO4(Ti4-/Ti3+) shows very good results, in which p·Si photocathode is stable.

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Effects of Humidity and Sliding Speed on the Wear Properties of $Si_3N_4$ Ceramics (습도 및 미끄럼 속도에 따른 질화규소의 마찰 마모 특성에 관한 연구)

  • 이기현;김경웅
    • Tribology and Lubricants
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    • v.9 no.2
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    • pp.63-69
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    • 1993
  • The wear properties of two types of $Si_3N_4$(silicon nitride) exposed to high and low humidity were examined experimentally for various sliding speed. Bearing steel was used as the disk material at pin-on-disk type sliding. Wear rates of pressureless sintered-plus-hot-isostatic pressed Si3N4 were slightly lower than those of pressureless sintered $Si_3N_4$. It was observed that adsorbed moisture and sliding speed markedly influenced the wear properties of $Si_3N_4$. The highest wear rate was obtained under the high humidity and low sliding speed condition. As the sliding speed was increased, wear rates were decreased and the humidity effect on the wear rates of $Si_3N_4$ was lowered. The result that the $Si_3N_4$ pin showed a high wear rate under the high humidity condition was explained by the property change due to the adsorbed moisture, plowing action by the hard particles of $Fe_2O_3$ from the disk, and the corrosion effect at $Si_3N_4$ surface. Increase in sliding speed was supposed to have reduced the humidity effect on wear rate of $Si_3N_4$ by raising the temperature of both the bearing steel disk and $Si_3N_4$ pin specimen.

Mechanical Properties of HfN/Si$_3$N$_4$and NbN/$Si_3N_4$Multilayer Coatings (HfN/Si$_3$N$_4$와 NbN/$Si_3N_4$다층박막의 기계적 특성)

  • Jeong, Jin-Jung;Hwang, Seon-Geun;Lee, Jong-Mu
    • Korean Journal of Materials Research
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    • v.11 no.3
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    • pp.236-242
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    • 2001
  • HfN/Si$_3$N$_4$and NbN/Si$_3$N$_4$ multilayer coatings were deposited onto a high speed tool steel substrate by reactive sputtering and their mechanical properties were evaluated in terms of the dependence of hardness and adhesion strength on the sputter deposition process parameters. The hardnesses of both HfN/Si$_3$N$_4$and NbN/Si$_3$N$_4$ multiplayer coatings increase up to the flux ratio of 0.4 but nearly do not change after that as the $N_2$/Ar flux ratio in nitride sputter deposition increases. The hardnesses of both multiplayer coatings nearly do not change with annealing at low temperatures but decrease owing to oxidation with annealing at a high temperature like 80$0^{\circ}C$ after depositing the layers by sputtering. Post-annealing at low temperatures increases the adhesion strength of the multilayers. but high temperature annealing is not desirable since it decreases the adhesion strength besides the hardness deterioration.

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