• 제목/요약/키워드: $Si_{3}N_{4}

검색결과 2,123건 처리시간 0.031초

Synthesis and Luminescence Properties of CaS:Eu2+,Si4+,Ga3+ for a White LED

  • Oh, Sung-Il;Jeong, Yong-Kwang;Kang, Jun-Gill
    • Bulletin of the Korean Chemical Society
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    • 제30권2호
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    • pp.419-422
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    • 2009
  • The luminescence intensity of calcium sulfide codoped with $Eu^{2+},\;Si^{4+}\;and\;Ga^{3+}$ was investigated as a function of the dopant concentration. An enhancement of the red luminescence resulted from the incorporation of $Si^{4+}\;and\;Ga^{3+}\;into\;CaS:Eu^{2+}.\;The\;non-codoped\;CaS:Eu^{2+}$ converted only 3.0% of the absorbed blue light into luminescence. As the $Si^{4+}\;and\;Ga^{3+}$ were embedded into the host lattice, the luminescence intensity increased and reached a maximum of Q = 10.0% at optimized concentrations of the codopants in CaS. Optimized CaS:$Eu^{2+},Si^{4+},Ga^{3+}$ phosphors were fabricated with blue GaN LED and the chromaticity index of the phosphor-formulated GaN LED was investigated as a function of the wt% of the optimized phosphor.

용탕단조법에 의한 휘스커강화 Al합금기 복합재료의 고속초소성 (High Strain Rate Superplasticity of Whisker Reinforced Aluminum Alloy Matrix Composites Fabricated by Squeeze Casting)

  • 임석원;유전의칙
    • 한국주조공학회지
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    • 제21권6호
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    • pp.359-365
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    • 2001
  • The superplastic behavior of whisker reinforced aluminum alloy matrix composites fabricated by squeeze casting as one of high pressure routes was investigated. The preforms of ${\alpha}-Si_3N_4$ and ${\beta}-SiC$ whiskers without any binder as a reinforcement were used. The matrix materials were 2024 and 7075 aluminum alloys. For the purpose of optimum superplastic condition, respectively, the whiskers volume fraction, extrusion temperature, tensile test temperature and initial strain rate were changed. Fracture surface of tested specimens were observed by SEM. By the results, it became possible to produce superplastic composites by applying only a hot extrusion process to composites obtained by the squeeze casting. The superplastic composites developed are ${\alpha}-Si_3N_4w/7075$, ${\alpha}-Si_3N_4w/2024$ and ${\beta}-SiCw/2024$ systems at high strain rate.

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ZnO-SnO2 투명박막트랜지스터의 동작에 미치는 게이트 절연층의 영향 (Effects of Gate Insulators on the Operation of ZnO-SnO2 Thin Film Transistors)

  • 천영덕;박기철;마대영
    • 한국전기전자재료학회논문지
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    • 제26권3호
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    • pp.177-182
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    • 2013
  • Transparent thin film transistors (TTFT) were fabricated on $N^+$ Si wafers. $SiO_2$, $Si_3N_4/SiO_2$ and $Al_2O_3/SiO_2$ grown on the wafers were used as gate insulators. The rf magnetron sputtered zinc tin oxide (ZTO) films were adopted as active layers. $N^+$ Si wafers were wet-oxidized to grow $SiO_2$. $Si_3N_4$ and $Al_2O_3$ films were deposited on the $SiO_2$ by plasma enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD), respectively. The mobility, $I_{on}/I_{off}$ and subthreshold swing (SS) were obtained from the transfer characteristics of TTFTs. The properties of gate insulators were analyzed by comparing the characteristics of TTFTs. The property variation of the ZTO TTFTs with time were observed.

Processing of $Si_3N_4/SiC$ and Boron-Modified Nanocomposites Via Ceramic Precursor Route

  • Lee, Hyung-Bock;Rajiv S. Mishra;Matt J. Gasch;Han, Young-Hwan;Amiya K. Mukherjee
    • The Korean Journal of Ceramics
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    • 제6권3호
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    • pp.245-249
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    • 2000
  • Consolidation of amorphous powders is emerging as a route for synthesis of high strength composite materials. Diffusion processes necessary for consolidation are expected to be more rapid in amorphous state(SRO) than in the crystalline state(LRO). A new synthesis technique of exploiting polymeric ceramic precursors(polysilazane and polyborosilazane) is derived for Si$_3$N$_4$/SiC and boron-modified nanocomposites for extremely high temperature applications up to 200$0^{\circ}C$. The characterization methods include thermal analysis of DTA, and XRD, NMR, TEM, after pyrolysis, as a function of time and temperature.

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Alkenylsilane의 제조와 고분자화반응 (Preparation and Polymerization of Alkenylsilanes)

  • 김정균;최순규;박은미;정인경
    • 대한화학회지
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    • 제41권2호
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    • pp.88-97
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    • 1997
  • 실릴트리플레이트$(Ph_{3-n}SiH(OTf)_n))$는 낮은 온도에서 트리펜일실란과 트리플산$(CF_3SO_3H)$의 반응에 의해 형성되며 이러한 화합물은 새로운 기능성 실란 유도체의 제조에 이용되고 있다. 실릴트리플레이트와 알캔일-, 알킨일마그네슘 브롬아이드 그리고 유기리티움 화합물과의 반응에 의해 새로운 실란 화합물 Ph_2SiHR(R=C{\equiv}(CPh,\;CH=CH_2,\;CH_2CH=CH_2,\;(CH_2)_2CH=CH_2,\;(CH_2)_3CH=CH_2)$을 높은 수율로 얻었다. 합성된 알켄일-, 알킨일실란은 백금촉매 하에서 카보실란 고분자$((Ph_2Si(CH_2)m)n;\;m=2∼4,\;n\le10)$5~6환고리 화합물을 형성하였다. 모든 생성물들은 NMR, UV, IR, 질량분석, 그리고 원소분석법에 의해 확인되었다.

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