• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.107-108
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• 2006

High $J_c$ $YBa_2Cu_3O_x$, superconducting films were fabricated by MOD method using fluorine-free dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. DCA-MOD precursor solution was coated on a single crystal (001) $LaAlO_3$(LAO) substrate by a dip coating method with a speed of 25 mm/min. Coated films were calcined at lower temperature up to $500^{\circ}C$ and Conversion heat treatment was performed at various temperatures of $780{\sim}810^{\circ}C$. SEM observations showed that films have very dense microstructures for the films prepared at the temperature higher than $800^{\circ}C$ regardless of diluting solvent; methanol or 2-methoxyethanol. A High critical current density ($J_c$) of 1.28 $MA/cm^2$ (@77 K and self-field) was obtained for the YBCO film prepared using 2-methoxyethanol as a solvent.

• Elastomers and Composites
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• 제48권4호
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• pp.288-293
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• 2013

무수말레산-그래프트 EPDM (MAH-g-EPDM)/산화아연 복합체를 디클로로아세트산(DCA)/톨루엔 공용매로 처리하고 추출 온도에 따른 무게 감소와 가교밀도 측정을 이용하여 가교 특성을 조사하였다. 감쇠전반-후리에변환 적외선분광법(ATR-FTIR)을 이용하여 화학적 변화를 분석하였다. 상온 추출보다 고온($90^{\circ}C$) 추출에 의한 무게 감소가 월등히 높았으며, DCA/톨루엔 공용매 추출에 의한 무게 감소는 톨루엔 추출에 의한 무게 감소보다 5배 이상 높았다. 용매 추출 후 가교밀도를 측정하였으며, 1차 가교밀도보다 2차 가교밀도가 높았다. 1차 가교밀도는 추출온도가 높은 경우 더 낮았고 DCA/톨루엔 공용매로 추출한 것이 톨루엔으로 추출한 것보다 훨씬 낮았다. 2차 가교밀도는 DCA/톨루엔 공용매로 추출한 것이 톨루엔으로 추출한 것보다 높았다. 고온에서 DCA/톨루엔 공용매로 추출하면 강한 가교 그물망만 남는 반면, 상온에서 톨루엔으로 추출하면 미가교 고분자 사슬이 추출되는 등 추출 용매와 온도에 따라 추출되는 성분이 달랐다. 따라서 추출 용매와 온도에 따른 추출 성분의 비교와 연속 가교밀도 측정에 의해 MAH-g-EPDM/산화아연 복합체의 가교 특성을 분석할 수 있다.

• Progress in Superconductivity
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• 제7권2호
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• pp.152-157
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• 2006

New precursor solution with dichloroacetic acid (DCA) was developed for fabricating high $J_c$ REBCO film. DCA based-precursor solution was coated on $LaAlO_3$(001) substrate by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature were controlled in order to obtain a good epitaxial film. The film with thickness of 0.5 micrometer was obtained by single coating and no crack was observed at calcined films. Oxygen partial pressure was controlled in the range of $100{\sim}1,000$ ppm and conversion heat treatment was carried out at the temperature range of $705-765^{\circ}C$. A critical transition temperature ($T_c$) of 90 K and a critical transport current density ($J_c$) of $>0.5\;MA/cm^2$ (77 K and self-field) were obtained for the GdBCO film. It is thought that fluorine-free MOD solution using DCA is promising precursor solution for fabricating high quality REBCO films.

• Progress in Superconductivity
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• 제8권1호
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• pp.59-64
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• 2006

High $J_c\;YBa_2Cu_3O_x$ superconducting films were fabricated by MOD method using fluorine-free dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Coating solutions were prepared by dissolving Y-, Ba- and Cu-acetates in DCA solvent followed by drying in rota vapor to obtain the blue gel that is diluted in methanol and 2-methoxyethanol for adjusting the cation concentration. DCA-MOD precursor solution was coated on a single crystal(001) $LaAlO_3(LAO)$ substrate by a dip coating method with a speed of 25 mm/min. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing oxygen atmosphere with a 7.2% humidity. Conversion heat treatment was performed at various temperatures of $780{\sim}810^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. SEM observations showed that films have very dense microstructures for the films prepared at the temperature higher than $800^{\circ}C$ regardless of diluting solvent; methanol or 2-methoxyethanol. X-ray diffraction analysis showed that YBCO grains grew with a (001) preferred orientation. A High critical current density($J_c$) of 1.28 $MA/cm^2$(@77 K and self-field) was obtained id. the YBCO film prepared using 2-methoxyethanol as a solvent.

• Progress in Superconductivity
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• 제8권2호
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• pp.186-192
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• 2007

High $J_c\;YBa_2Cu_3O_{7-x}$ superconducting films have been fabricated $LaAlO_3(100)$ substrate by MOD method using dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Heating rate was varied in order to optimize the calcination heat treatment condition in DCA-MOD method. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing humid oxygen atmosphere. The heating rate was calcined from $13.3^{\circ}C/min\;to\;0.28^{\circ}C/min$. Conversion heat treatment was performed $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Surface and cross sectional SEM microstructures showed that particle sizes were increased with heating rate at a calcination step. The amount of pores was increased with heating rate in the calcined films. Dense microstructure and sharp texture were developed in an YBCO films after conversion heat treatment. A high critical current density (Jc) of $1.26MA/cm^2$ (@77 K and self-field) was obtained for the YBCO film which was prepared with a heating rate of $0.28^{\circ}C/min$.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2006년도 High Temperature Superconductivity Vol.XVI
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• pp.37-37
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• 2006

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.45-52
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• 1995

광 촉매로 널리 알려진 TiO$_2$의 광 분해 거동의 변화를 관찰하기 위하여 Nb$_2$O$_{5}$를 첨가하여 sol-gel 용법으로 제조한 후 DCA(dichloroacetic acid) 의 광분해 효율을 측정하였다. Sol-gel process 과정에서 첨가된 Nb$_2$O$_{5}$의 농도 및 열처리 온도변화에 따른 광분해 효율을 관찰한 결과, Nb$_2$O$_{5}$를 첨가한 후 40$0^{\circ}C$에서 한시간 동안 열처리 한 광 촉매의 광분해 효율이 가장 높게 나타났다. 또한 열처리 온도와 무관하게 Nb$_2$O$_{5}$의 양이 증가할수록 광분해 효율은 감소하는 것으로 관찰되었다. 이는 excess electron 의 증가로 환원 반응 혹은 recombination rate기 증가하기 때문이라고 사료된다. 분해 대상 물질의 pH가 낮을수록 광분해 효율이 증가하는 것을 알 수 있었다.알 수 있었다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.31-40
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• 1995

The degradation of aqueous chlorinated compounds such as trichloroethylene (TCE), tetrachloroethylene (PCE) and dichloroacetic acid (DCA) to $CO_2$ and HCl was accomplished in the presence of UV light and suspended TiO$_2$ slurries. The decomposition of chlorinated hydrocarbons at 253.7 m irradiation was more effective than that at 360 nm irradiation. Our results show that 253.7 nm irradiation alone can be used for decomposing some chlorinated hydrocarbons such as PCE and TCE.

• 한국재료학회지
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• 제6권3호
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• pp.282-290
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• 1996

광화학 반응의 초기 유발을 위한 광촉매로 TiO2가 가장 널리 알려져 있으며, 기존의 상품보다 광촉매 활성도가 높은 촉매를 얻기 위해 Sol-Gel법을 이용하였다. TiO2 광촉매 제조를 위하여 전구체로서 Tetra-eth해-ortho-titanate(TEOT)를 이용하여 xerogeol 분말을 얻었으며, 광화학 반응의 효율을 측정하기 위해 분해대상 물질을 Dichloroacetic acid(DCA)로 선정하였다. 순수 titania 졸을 얻기 위한 최적조건은 알콕사이드 1몰당 물 40몰, 산 0.05몰이었고 pH의 범위는 3.3-3.6이었으며 Hexylene Glycol(HG)의 첨가량은 1몰임을 알 수 있었다. BET-N2방법을 이용하여 표면적을 측정한 결과 물/알콕 사이드의 몰비가 40-80범위에서 비표면적이 급격히 증가되어 DCA 의 광분해율도 증가하였으며, 몰 40몰을 첨가 후 졸-겔법으로 제조한 분말을 40$0^{\circ}C$에서 1시간 열처리한 anatase phase의 TiO2가 최고의 광분해 효율인 약 21%를 보였다. 이는 상업용으로 가장 효율이 높은 Dagussa P-25의 DCA 분해 효율보다 2배 정도 높은 것으로 나타났다.

• 한국응용과학기술학회지
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• 제23권2호
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• pp.99-109
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• 2006

In order to obtain the maximum flame retardancy as well as the minimum deterioration of physical properties of PU flame-retardant coatings, chlorine and phosphorus functional groups were introduced into the pre-polymer of modified polyesters. In the first step, the tetramethylene bis(orthophosphate) (TBOP) and neohexanediol dichloroacetate (DCA-adduct) intermediates were synthesized. In the second step, 1,4-butanediol and adipic acid monomers were polymerized with the two kinds of intermediates to obtain copolymers. The modified polyesters containing chlorine and phosphorus (ATBA-10C, -20C, and -30C) were synthesized by adjusting that the content of phosphorus compound was fixed as 2wt% and the contents of chlorine compound (dichloroacetic acid) were varied as 10, 20, and 30wt%. Average molecular weight and polydispersity index of the preparation of ATBAs were decreased with increasing DCA content because of the increase in hydroxyl group that retards reaction.