• 한국표면공학회지
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• 제27권4호
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• pp.207-214
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• 1994

In consideration of global environmental protection and fuel saving, aluminum alloy sheets for auto body panels such as hood, fender etc., are expected one of the most promising materials for weight saving of cars. The chemical conversion coating is required to prevent the filiform corrosion occurring on painted aluminum. However the conventional process for the composited material mixed with aluminum and steel is complexs; aluminum part is chromated and assembled to the body, and then the steel body undergoes Zn phosphating. In order to overcome the low productivity due to the complex process and the environmental problem with a conventional process, a simultaneous zinc phosphating process for alsuminum and steel in an assembled condition is demanded. Newly developed phosphate solution has been investigated to characterize the phosphating behavior under various conditions. The optimum conditions of the phosphating solution for the application of the paint treatment derived as follows : about 0.3 for the ratio of Zn to $PO_4$, , 200~500 ppm for the concentration of fluoride ion, and 2.5~4.0 for pH. The concentration of dissolved aluminum ion must be kept below 2--ppm and suitable accelerator is found to be a mixture of 1g/$\ell$ $NO_2\;^-$, and 6g/$\ell$ $NO_3\;^-$.

• 대한소아치과학회지
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• 제37권1호
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• pp.35-43
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• 2010

본 연구는 젤라틴과 메틸셀룰로오스를 기저재로 한 불소겔을 제작하고 이들의 높은 점조도와 표면에 흡착하는 능력이 치면에 불소를 오랜 시간 저류시켜 법랑질 탈회를 효과적으로 억제할 수 있는지 살펴보고자 시행되었다소의 전치로 시편 80개를 제작하였으며, (1) APF gel (2) $CavityShield^{TM}$, (3) Gelatin F gel (4) Methyl cellulose F gel 이렇게 4개의 군으로 분류하였다. 모든 시편을 인공우식용액에 72시간동안 보관하여 법랑질을 탈회시킨 후, 표면미세경도 측정법과 편광 현미경하에서 병소의 탈회 깊이를 측정하는 두 가지 방법을 사용하여 탈회정도를 측정하였다. 연구결과는 다음과 같다. 1) 불소를 처리한 experimental side와 처리하지 않은 control side간 미세경도의 차이는 APF를 적용한 제1군에서 71.82(VHN)로 가장 작은 것으로 나타났다(p<0.05). 2) $CavityShield^{TM}$를 도포한 제2군에서 148.24(VHN)로 가장 큰 차이를 보여 불소바니쉬의 탈회억제효과가 가장 큰 것으로 나타났다(p<0.05). 3) Gelatin과 methyl cellulose F gel을 도포한 3군과 4군에서 control side와 experimental side간 미세경도의 차이는 1군보다는 높고 2군보다는 낮았으나 3군과 4군간에 유의한 차이는 없었다(p>0.05). 4) 인공탈회병소의 깊이를 측정한 결과 APF를 처리한 제1군에서 control side와 experimental side간 병소의 깊이차이는 $16.69\;{\mu}m$로 가장 적게 나타났다(p<0.05). 5) 2,3,4군 에서는 병소깊이 측정을 통해 탈회억제효과가 APF군에 비해 우수하게 나타났으나(p<0.05) 각 군 간에 차이는 검증되지 않았다(p>0.05). 이상의 결과를 종합하여 보면 실험적으로 제조된 두 가지 불소겔은 APF gel에 비해 법랑질 탈회 억제효과가 우수하다고할 수 있으며 이는 APF gel에 비해 gelatin이나 methyl cellulose 의 높은 점조도가 불소를 더 장시간 치면에 접촉시킨 것으로 생각된다. 현재 가장 우수한 치면 잔류시간을 보이는 것으로 인정되는 불소바니쉬와 비교하여도 이들의 효과가 크게 떨어지지 않는 것을 알 수 있었으며 이는 향후 천연고분자 화합물을 이용한 다양한 불소제제의 개발 가능성을 보여주는 것이라 사료된다.

• Membrane and Water Treatment
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• 제10권4호
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• pp.287-298
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• 2019

Lotus leaf has a special dual micro and nano surface structure which gives its highly hydrophobic surface characteristics and so-called self cleaning effect. In order to endow PVDF hollow fiber membrane with this special structure and improve the hydrophobicity of membrane surface, PVDF hollow fiber composite membranes was obtained through the immersion coating of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) dilute solution on the outside surface of PVDF support membrane. The prepared PVDF composite membranes were used in the vacuum membrane distillation (VMD) for the desalination. The effects of PVDF-HFP dilute solution concentration in the dope solution and coating time on VMD separation performance was studied. Membranes were characterized by SEM, WCA measurement, porosity, and liquid entry pressure of water. VMD test was carried out using $35g{\cdot}L^{-1}$ NaCl aqueous solution as the feed solution at feed temperature of $30^{\circ}C$ and the permeate pressure of 31.3 kPa. The vapour flux reached a maximum when PVDF-HFP concentration in the dilute solution was 5 wt% and the coating time was kept in the range of 10-60 s. This was attributed to the well configuration of micro-nano rods which was similar with the dual micro-nano structure on the lotus leaf. Compared with the original PVDF membrane, the salt rejection can be well maintained which was greater than 99.99 % meanwhile permeation water conductivity was kept at a low value of $7-9{\mu}S{\cdot}cm^{-1}$ during the continuous testing for 360 h.

• 공업화학
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• 제20권5호
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• pp.557-560
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• 2009

본 연구에서는 글라스를 $100{\mu}m$ 이하의 두께로 박판화하기 위한 새로운 습식 에칭방법 및 에칭 용액을 검토하였다. $NH_4F$ 또는 $NH_4HF_2$를 주성분으로 황산 또는 질산을 첨가한 경우 에칭 용액의 불산 함유량을 저감하는 데에 효과가 있었다. 혼산 용액의 조성과 온도의 영향을 검토하였으며, 음이온계 계면활성제의 첨가는 에칭반응에 의해 생성되는 슬러지의 부착을 억제해주는 효과가 있었다. 수류 발생부를 가지는 새로운 파일럿 장비를 사용하여 상용 무알칼리 글라스와 소다라임 글라스의 에칭 실험을 실시하였다. $640{\mu}m$ 두께의 무알칼리 글라스를 $45{\mu}m$ 두께로 $500{\mu}m$ 두께의 소다라임 글라스를 $100{\mu}m$ 두께로 박판화하였으며, 에칭 후의 표면 조도는 $0.01{\sim}0.02{\mu}m$를 유지하였다.

• Korean Chemical Engineering Research
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• 제59권4호
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• pp.632-638
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• 2021

반도체 공정에서 구리 배선 공정의 도입에 따라 플라즈마 식각에 의해 배선의 형성과정에서 구리 산화물, 불화물 및 불화탄소 등을 포함한 복합 잔류물을 형성하게 된다. 본 연구에서는 아민기(-NH₂)와 카르복실기(-COOH)를 갖는 성분으로 세정액을 제조하여 구리 배선 공정에서의 식각 잔류물 제거 특성을 분석하였다. 아민기를 포함한 세정액은 질소에 치환된 성분 및 탄소결합의 길이에 따라 세정효과에 차이를 보이며, 세정액의 pH가 증가함에 따라 구리 산화물의 식각 속도가 증가하는 경향성을 보였다. 아민기의 활성은 염기성 영역에서, 카르복실기의 활성은 산성 영역에서 이루어지며, 각각의 영역에서 구리 또는 구리 산화물과의 complex 형성을 통하여 세정공정이 진행되었다.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.167-171
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• 2004

The electroless deposition of copper on the hydrogen-terminated Si(111) surface was investigated by means of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning tunneling microscopy (STM), and energy-dispersive spectroscopy (EDS). The hydrogen-terminated Si(111) surface prepared was stable under air atmosphere for a day or more. It was found from ATR-FTIR that two bands centered at 2000 and 2260 $cm^{-1}$ appeared after the H-Si(111) surface was immersed in 40% $NH_4F$ solution containing 10 mM $Cu^{2+}$. On the other hand, STM image included the copper islands with a height of 5 nm and a diameter of 10-20 nm. The EDS data displayed the presence of copper, silicon and oxygen species. The results were rationalized in terms of the redox reaction of surface Si atoms and $Cu^{2+}$ ions in solutions, which are changed into $Si(OH)_x(F)_y$ containing $SiF_6^{2-}$ ions and neutral copper islands.

• 한국염색가공학회지
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• 제4권2호
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• pp.76-83
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• 1992

Wool tropical and nylon taffeta were treated with low temperature plasma of $O_2$, $N_2$, NH$_3$, CF$_4$ and CH$_4$ for the intervals of 10 to 300 sec, and then dyed with leveling and milling type acid dyes in presence or absence of buffer solution. From the color depth of dyed fabrics, effect of plasma gases, treated time, dyeing time and temperature on dyeing property was studied. The results of the experiment can be summarized as follows: 1) The plasma treatments except methane gas increased the color depth of dyed wool fabrics, but not that of dyed nylon fabrics regardless of the plasma gases used. 2) The color depth of wool fabrics dyed in the dye bath without buffer solution was increased by the low temperature plasma, especially increased much more by CF$_4$ plasma treatment. It is found that with the identification of F- ion in the residual dye bath the hydrogen fluoride gas was adsorbed on wool fabrics in the plasma treatment. 3) The color depth of wool fabrics was increased with the time of $O_2$ and CF$_4$ plasma treatments. 4) In both cases of the leveling and milling type acid dyes, the rate of dyeing was increased in the low temperature plasma treatments, and it is found that the leveling type acid dye increased the color depth at relatively low temperature below 4$0^{\circ}C$, compared with the milling type acid dye.

• 전기학회논문지
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• 제62권8호
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• pp.1115-1119
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• 2013

The carbon nanotube/poly-vinylidene fluoride (CNT/PVDF) composite films for the use of electronic devices were fabricated by spray coating method using the CNT/PVDF solution, which was prepared by adding PVDF pellets into the CNT dispersed N-Methyl-2-pyrroli-done (NMP) solution. The CNT/PVDF composite films were peeled off from the glass substrate and were investigated by the scanning electron microscopy, which revealed that the CNTs were uniformly dispersed in the PVDF films and thickness of the films were approximately $20{\mu}m$. The capacitance of the CNT/PVDF films increased dramatically by adding CNTs into the PVDF matrix, and finally saturated approximately 1880 pF. However, the I-V curves didn't show any saturation effect in the CNT concentration range of 0 ~ 0.04 wt%. Therefore we can control the performance of the devices from the CNT/PVDF composite film by adjusting the current level resulted from the CNT concentration with the uniform capacitance value.

• 한국환경과학회지
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• 제19권11호
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• pp.1315-1322
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• 2010

A membrane bioreactor (MBR) was designed using polyvinylidene fluoride(PVDF)-type hollow fiber membrane modules with a treatment capacity of 10 ton/day. A pilot plant was installed in a sewage treatment plant and was operated with an intermittent aeration method which avoids any concentration gradient of suspended solids (SS) in the MBR. For continuous operation, the pilot plant was first tested with influent (mixed liquor suspended solid:MLSS of 1000-2000 mg/L) of aeration tanks in the sewage treatment plant. The MBR was pre-treated with washing water, 10% ethanol solution, 5% NaOCl solution and finally washing water, one after another. To demonstrate the effect of the MBR on sewage treatment, compared with conventional activated sludge processes, we investigated the relationships among permeate amount (LMH), change in operation conditions, influent MLSS level and sludge production. It was found that the optimum aeration rate and suction pressure were $0.3\;m^3$/min and 30~31 cmHg, respectively. Under stable conditions in aeration, suction pressure, influent flow rate and drainage, the SS removal efficiency was more than 99.99% even when the MLSS loading rate changes. Compared with conventional activated sludge processes, the MBR was more effective in cost reduction by 27% based on permeate amount and by 51.5% on sludge production.

• 한국전기전자재료학회논문지
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• 제26권8호
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• pp.620-623
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• 2013

The carbon nanotube / poly-vinylidene fluoride (CNT/PVDF) composite films for the nano-generator devices were fabricated by spray coating method using the CNT/PVDF solution, which was prepared by adding PVDF pellets into the CNT dispersed N-Methyl-2-pyrroli-done (NMP) solution. The flexible CNT/PVDF composite films were investigated by the scanning electron microscopy, which revealed that the CNTs were uniformly dispersed in the PVDF matrix and thickness of the films was approximately $20{\mu}m$. Fourier transform infra-red spectra were used to investigate crystal structure of the as-spray-coated CNT/PVDF films, and we found that they revealed extremely large portion of the ${\beta}$ phase PVDF. The capacitance of the CNT/PVDF films increased by adding CNTs into the PVDF matrix, and finally saturated. However, the resistance didn't show any saturation effect in the CNT concentration range of 0~4 wt%. Finally, the resulting nano-generator devices revealed reasonable current output after given mechanical stress.