• Corrosion Science and Technology
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• v.14 no.4
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• pp.166-171
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• 2015

Knowledge of how metal releases from the stainless steels used in food processing applications and cooking utensils is essential within the framework of human health risk assessment. A new European standard test protocol for testing metal release in food contact materials made from metals and alloys has recently been published by the Council of Europe. The major difference from earlier test protocols is the use of citric acid as the worst-case food simulant. The objectives of this study were to assess the effect of citric acid at acidic, neutral, and alkaline solution pH on the extent of metal release for stainless steel grades AISI 304 and 316, commonly used as food contact materials. Both grades released lower amounts of metals than the specific release limits when they were tested according to test guidelines. The released amounts of metals were assessed by means of graphite furnace atomic absorption spectroscopy, and changes in the outermost surface composition were determined using X-ray photoelectron spectroscopy. The results demonstrate that both the pH and the complexation capacity of the solutions affected the extent of metal release from stainless steel and are discussed from a mechanistic perspective. The outermost surface oxide was significantly enriched in chromium upon exposure to citric acid, indicating rapid passivation by the acid. This study elucidates the effect of several possible mechanisms, including complex ion- and ligand-induced metal release, that govern the process of metal release from stainless steel under passive conditions in solutions that contain citric acid.

• Journal of Adhesion and Interface
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• v.19 no.4
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• pp.163-166
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• 2018

Dip-pen nanolithography(DPN) is an atomic force microscope (AFM) based method of generating nano- or micro-patterns. This technique has been used to transfer various ink materials on the substrate through water meniscus formed between AFM tip and the substrate surface. In this study, the heptadecafluoro-1,1,2,2-tetrahydrodecyltrimethoxysilane (HDFDTMS) ink materials were coated on the pre-coated AFM tip surface with the HDFDTMS molecules. When the tip brought into contact with the hydroxyl-functionalized silicon surface, HDFDTMS ink molecules have been successfully transported from the tip onto the surface via water meniscus. The created array and passivation area showed stable structures on the surface, and the transport of ink materials from the AFM tip to the surface followed linear increase in pattern size with contact time.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.439-440
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• 2002

Nano-Crystalline $CeO_2$ particles were dispersed in deionized water with controlled slurry chemicals for CMP test. According to the CMP test, the removal rate of $SiO_2$ layer was mainly controlled by the size and crystallinity of $CeO_2$ particles which can be controlled by the heat-treatment condition during $CeO_2$ synthesis. In contrast, the removal rate of $Si_3N_4$ layer was significantly influenced by the passivation reagent which protects the $Si_3N_4$ surface layer from excessive dissolution during CMP.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.417-417
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• 2012

For desired optical properties of QDs, it is very important to reduce the presence of defects on their surfaces. Passivation of surface defects using larger band gap materials is the most effective way. Some groups successfully synthesized Cd based multi-shell structured quantum dots and improved its optical properties. However, its productivity has limit because of the amounts of glass ware and space. In this research, we try to synthesize Cd based multi-shell structured nanocrystal quantum dots to overcome demerits of conventional batch synthetic method. This reactor composed pump, SUS reaction part (3.2 mm stainless steel and furnace) and batch mixer. We successively synthesized CdSe/CdS/ZnS quantum dot at this reactor in one step.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.755-760
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• 2001

본 연구에서는 카본전극의 표면개질에 따른 리튬이온 전지의 전지특성 변화에 대해서 연구하였다. 즉, mesocarbon microbeads(MCMB) 카본에 에폭시 수지(resin)를 코팅시킴으로서 카본전극 표면에 개질시켰으며, 이에 따른 전극의 전기화학적 특성을 고찰하였다. 에폭시 수지에 의한 카본의 표면코팅은 30%의 H$_2$SO$_4$용액에서 2시간 동안 refluxing한 MCMB를 에폭시 수지를 용해시킨 THF(tetrahydrofuran) 용액에 넣어 혼합함으로써 MCMB 표면에 에폭시 수지가 코팅되도록 하였다. 이렇게 에폭시 수지가 코팅된 MCMB를 약 1000-130$0^{\circ}C$로 열처리하여 고분해능 투과전자현미경으로 관찰한 결과, 코팅층은 비정질 카본 구조를 갖게됨을 알 수 있었다. 또한, 에폭시 수지에 의하여 코팅된 MCMB는 코팅되지 않은 MCMB보다 더 높은 BET 비표면적을 나타내었다. Li/MCMB 전지 cell을 만들어 충방전시험을 수행한 결과, 에폭시 수지에 의하여 코팅된 MCMB로 만든 전극이 더 우수한 충방전 용량과 싸이클 특성을 나타내었다. 에폭시 수지 코팅으로 전극 표면을 개질시킴으로서 전지특성이 개선된 원인에 관하여 에폭시 코팅의 결정구조와 전극계면에서의 부동태 피막(passivation film) 형성과 연계하여 논의하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.334-338
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• 2006

Poly silicon TFT requires high quality dielectric film; conventional method of growing silicon dioxide needs highly hazardous chemicals such as silane. We have grown high quality dielectric film of silicon dioxide using non-hazardous chemical such as TFOS and ozone as reaction gases by APCVD. The films grown were characterized through C-V curves of MOS structures. Conventional APCVD requires high temperature processing where as in the process of current study, we developed a low temperature process. Interface trap density was substantially decreased in the silicon surface coated with the silicon dioxide film after annealing in nitrogen ambient. The interface with such low trap density could be used for poly silicon TFT fabrication with cheaper cost and potentially less hazards.

• Korean Journal of Crystallography
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• v.14 no.2
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• pp.56-61
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• 2003

Nanocrystalline hydrogenated silicon (nc-Si : H) thin films were deposited at room temperature by plasma enhanced chemical vapor deposition (PECVD): a mixture of SiH₄ and H₂ gas was introduced into the evacuated reaction chamber. When the H₂ gas flow rate was low, the density of Si-H₃ bonds was high in the films. On the other hand, when the H₂ gas flow rate was high, e.g., 100 sccm, a large number of Si-H bonds contributed to the passivation of the surface of the large volume of Si nanocrystallites. The relative fraction of the Si-H₃ and Si-H₂ bonds in the amorphous matrix varied sensitively with the H₂ gas flow rate. The variation was associated with the change in the intensity as well as the wavelength of the main PL peaks, indicating the change in the total volume as well as the size of the Si nanocrystallites in the films.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1905-1907
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• 2001

본 논문에서는 다공질 실리콘에 대한 에탄올과 메탄을 가스 감지 특성을 측정하고 전기 전도도의 변화를 고찰하였다. 우선 HF와 에탄올의 혼합 용액내에서 n-type의 웨이퍼에 일정 전압을 인가하여 다공질 실리콘을 형성한다. 다공질 실리콘은 수직한 방향으로 $55{\sim}60{\mu}m$ 두께로 균일하게 형성되었다. 다공질 실리콘을 이용하여 소자를 제작하고 에탄올과 메탄올 가스를 주입하여 전류-전압 특성을 측정하였다. 기존의 다공질 실리콘 에탄올 센서와는 달리 turn-on 시 센서에 흐르는 전류가 빠른 시간내에 일정한 값으로 도달하였고 turn-off시에도 같은 결과를 보였다. 다공질 실리콘 표면에 흡착된 에탄올과 메탄올 가스는 전류의 흐름을 방해하는 surface charge를 스크린하여 전기 전도도를 증가시킨다. 또한 흡착된 가스가 dangling bonds를 passivation하여 전류를 증가시키는 것으로 생각된다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.2
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• pp.55-62
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• 1992

Polycrystalline silicon ingots were manufactured using the casting method for polycrystalline silicon solar cells. These ingots were cut into wafers and ten n$^{+}$p type solar cells were made through the following simple process` surface etching, n$^{+}$p junction formation, metalization and annealing. For the grain boundary passivation, the samples were oxidized in O$_2$ for 5 min. at 80$0^{\circ}C$ prior to diffusion in Ar for 100 min. at 95$0^{\circ}C$. The conversion efficiency of polycrystalline silicon solar cells made from these wafers showed about 70-80% of those of the single crystalline silicon solar cell and superior conversion efficiency, compared to those of commercial polycrystalline wafers of Wacker Chemie. The maximum conversion efficiency of our wafers was indicated about 8%(without AR coating) in spite of such a simple fabrication method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.288-291
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• 1996

The surface properties after plasma etching of TiW solutions using the chemistries of BCl$_3$ and SF$\_$6/ gases with varying mixing ratio have been investigated using X-ray photoelectron spectroscopy. The elements of C, Cl, F, O and S are observed on the etched TiW films. After plasma etching with SF$\_$6/ gas, Ti-S bond are detected on the samples and Ti-S bond makes a role of passivation layer that surpresses Ti-O formation. After plasma etching wish BCl$_3$ gas, Ti are easily removed but W are hardly etched. As a results, W/Ti are increased on the etched sample.