• 대한전자공학회논문지
• /
• 제26권8호
• /
• pp.1197-1202
• /
• 1989

In this study, physical properties of silicon dioxide film deposited on GaAs by photo excitation are evaluated using ellisometry, ESCA and AES. Under the pressure of 2-8 torr, silicon dioxide film is deposited on GaAs by photo excitation at 200\ulcorner using gas mixtures of SiH4 and N2O. The measured results show refractive index varies from 1.37 to 1.42 and stoichiometry from 1.97 to 2.09 with process pressure. The observed characteristics of deposition rate are divided into three different regions with process pressure and possible deposition mechanism are also discussed, qualitatively.

• 자원리싸이클링
• /
• 제21권2호
• /
• pp.47-52
• /
• 2012

콘크리트 구조물 형식의 다양화에 따라 요구되는 콘크리트의 품질 또한 고성능화가 필수적으로 되고 있다. 콘크리트의 고성능화는 혼화재료의 사용을 통하여 도달되고 있는데 일반적으로 고강도 콘크리트를 제작하기 위해서는 실리카 흄을 사용하고 있다. 실리카 흄은 역학적 성능은 우수하나 경제적 이지 못해 최근 이의 대체재로서 메타카올린의 연구가 많이 진행되고 있다. 본 연구는 실리카 흄의 대체재로 메타카올린을 사용하였으며 이에 따른 유동성의 저하를 방지하기 위해 이산화규소를 사용한 콘크리트를 제작하여 각 종 역학적 특성을 검토하였다.

• 대한화학회지
• /
• 제41권10호
• /
• pp.541-546
• /
• 1997

이산화망간 존재하에서 사염화규소는 1차, 2차, 3차 및 벤질알코올 유도체 뿐 만 아니라 시클로헥산올과 같은 고리형 알코올, 알릴 알코올 등의 염소화반응을 정량적으로 수행할 수 있음을 발견하였다. 먼저 이산화망간이 사염화규소의 반응성이 큰 규소-염소 결합에 삽입되어 불안정한 중간체인 Manganese(IV) oxodichloride를 생성하고 이 중간체는 계속하여 사염화규소와 반응하여 최종적으로 사염화망간을 생성하리라 예상된다. 이렇게 생성되리라 예상되는 화학종들은 모두 반응메카니즘적으로 알코올의 염소화반응에 관여할 수 있음을 알았다. 이 반응은 Thionyl chloride나 삼염화인등을 사용한 고전적인 알코올의 염소화반응에 비하여 많은 장점을 가짐을 알 수 있었다.

• 분석과학
• /
• 제21권5호
• /
• pp.397-402
• /
• 2008

이산화우라늄을 질산 및 미량의 불산으로 녹인 다음 우라늄 매트릭스로부터 규소를 분리하지 않고 분광광도계(spectrophotometer)로 측정할 수 있는 분석조건을 검토하였다. 분광광도계로 미량의 규소를 측정할 때 미량의 불산이 규소 분석에 미치는 영향을 조사하였으며, 불산의 간섭을 방지하기 위하여 붕산을 사용하였다. 우라늄 용액에서 미량의 불산이 존재할 경우 포화붕산 사용 유무에 따른 규소의 회수율은 각각 $103.3{\pm}0.8$ 및 $76.6{\pm}6.8%$이었다. 포화붕산의 양은 규소의 회수율에 크게 영향을 미치지 않았다. 따라서 본 방법으로 이산화우라늄 분말 중의 불순물로 존재하는 미량의 규소를 분리 과정없이 바로 UV-VIS 분광광도법으로 정량할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.39-39
• /
• 2009

We fabricated p-channel TFTs based on poly Silicon. The 35nm thickness silicon dioxide layer structure got higher $I_{on}/I_{off}$ ratio, field-effect Mobility and output current than 10nm thickness. And 35nm layer showed low leakage current and threshold voltage. So, 35nm thickness silicon dioxide layer TFTs are faster reaction speed and lower power consumption than 10nm thickness.

• 한국산업보건학회지
• /
• 제26권2호
• /
• pp.119-138
• /
• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 1997년도 제13회 학술발표회 논문개요집
• /
• pp.63-63
• /
• 1997

• Environmental Engineering Research
• /
• 제16권3호
• /
• pp.159-164
• /
• 2011

This study examined the emission characteristics of impure gas-like hydrogen sulfide and siloxane contained in landfill gas (LFG) and investigated the effect of impure gas on LFG utility facilities. As a result of an LFG component analysis from eight landfills in the same environment, hydrogen sulfide averaged 436 ppmv (22-1,211 ppmv), and the concentration of total siloxane averaged 7.95 mg/$m^3$ (1.85-21.18 mg/$m^3$). In case of siloxane concentration by component, the ratio of D4 (average 3.79 mg/$m^3$) and D5 (average 2.64 mg/$m^3$) indicated the highest level. Different kinds of scales were found on the gas air heater (GAH) and inside the boiler. The major component of scale from the GAH was $Fe_2O_3$ of 38.5%, and it was caused by hydrogen sulfide. Other scale was found on the bottom and the wall of the boiler and the scale was silicon dioxide of 92.8% and 98.9%. The silicon dioxide scale was caused by combustion of siloxane. As a result of a scanning electron microscopy analysis, the structure of the silicon dioxide scale from the boiler was an immediate filamentous type. Consequently, as silicon dioxide scale is bulky, such bad effects were worsening, as an interruption in heat conduction, increase in fuel consumption, damage to the boiler by overheating, and clogged emission pipeline could occur in LFG utility facilities.

• Nuclear Engineering and Technology
• /
• 제55권10호
• /
• pp.3725-3731
• /
• 2023

Thorium dioxide (ThO₂)-silicon carbide (SiC) composite fuel pellets were fabricated via the spark plasma-sintering (SPS) method to investigate the role of the addition of SiC in enhancing the thermal conductivity of ThO₂ fuel. SiC particles with an average size of 1㎛ in 10 and 15 vol% were used to manufacture the composite pellets. The changes in the composites' densification, microstructure and thermal conductivity were explored by comparing them with pure ThO₂ pellets. The structural and microstructural characterization of the composite pellets has revealed that SPS could manufacture high-quality composite pellets without having any reaction products or intermetallic. The density measurement by the Archimedes principles and the grain size from the electron back-scattered diffraction (EBSD) analysis has indicated that the composites have higher densities and smaller grain sizes than the pellets without SiC addition. Finally, thermal conductivity as a function of temperature has revealed that sintered ThO₂-SiC composites showed an increase of up to 56% in thermal conductivity compared to pristine ThO₂ pellets.

• Bulletin of the Korean Chemical Society
• /
• 제32권8호
• /
• pp.2560-2564
• /
• 2011

Mesoporous silicon dioxide (meso-$SiO_2$) was prepared using cetyltrimethylammonium bromide as the structure-directing reagent and tetraethyl orthosicate as the silicon source. The influence of pH value on the adsorption behavior of bisphenol A (BPA) was investigated. The adsorption capacity of BPA onto meso-$SiO_2$ increases slightly with pH value from 2 to 6, and then gradually decreases as further improving pH value. The effect of temperature was also studied, and the adsorption capacity of BPA gradually declines with increasing temperature. The adsorption kinetics and thermodynamics of BPA were examined. It is found that the adsorption of BPA onto meso-$SiO_2$ is in good agreement with Langmuir adsorption model. The rate constant of adsorption is $5.17{\times}10^{-3}g\;mg^{-1}\;min^{-1}$, and the maximum adsorption capacity is as high as 353.4 $mg\;g^{-1}$ at 20 $^{\circ}C$.