• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.307-310
• /
• 2007

We describe effects of ionic and neutral additives on phase and structural behavior of the lyotropic chromonic liquid crystals used in preparation of optical elements such as polarizers and compensators.

• 공업화학
• /
• 제27권5호
• /
• pp.516-520
• /
• 2016

농축세정제는 일반세정제의 2배~3배 농도의 계면활성제를 사용하여 제조하며, 계면활성제가 35~45% (w/w) 정도가 된다. 일반적으로 단일 계면활성제는 농도의존적으로 30~60% (w/w) 영역에서 액정상을 형성한다고 알려져 있다. 혼합 계면활성제 시스템인 약 40% (w/w) 전후 농도의 농축세정제는 외관이 불투명하거나 겔상의 액정상을 형성한다. 소비자가 선호하고 사용하기 적합한 제품화를 위해 투명상과 영하의 온도에서도 clear한 상을 얻기 위해서 하이드로트로프(hydrotrope)를 적용하였으며, 효과가 우수한 하이드로트로프는 1,6-hexanediol, adipic acid와 dipropylene glycol와 같은 분자 양말단에 친수기를 가진 타입이었다. 점도가 조절되고 저온에서 상안정성이 우수한 농축세정제를 제조하기 위해서는 우수한 하이드로트로프와 함께 LAS와 SAS 같은 친수기가 계면활성제 소수기의 중간에 위치한 secondary type의 계면활성제를 적용하는 것이었다. 양말단에 친수기가 있는 하이드로트로프와 secondary type 계면활성제를 혼합 적용함으로써 약 40% (w/w) 농도의 농축세정제의 액정형성을 방지할 수 있다. 본 기술의 적용으로 저온안정성이 우수하며 점도가 적당히 조절된 농축세정제의 제조가 가능하다.

• 한국결정성장학회지
• /
• 제30권4호
• /
• pp.150-155
• /
• 2020

구조용 세라믹재료로 주로 사용되는 알루미나(Al₂O₃)는 우수한 기계적 특성을 위해 치밀한 미세구조를 요구하며, 소결온도를 낮추기 위해 상업적으로 액상소결(liquid phase sintering)이 적용된다. 본 연구에서는 SiO₂, MgO, CaO를 액상소결 조제로 사용하는 92 % 상업용 알루미나의 액상소결 시, 착색제(coloring agent)로 주로 사용되는 산화코발트(Co₂O₃)의 첨가량과 다양한 소결온도가 알루미나의 미세구조 및 기계적 특성에 미치는 영향을 고찰하였다. 약 11 w t% 산화코발트 첨가에 따라 1200℃부터 고상입자 재배열에 의한 수축이 시작되었고 1300℃ 이상의 온도에서 용해 재석출 및 합체(coalescence)에 의한 알루미나의 결정립 성장이 관찰되었다. 1400℃ 이상의 열처리 온도 혹은 과량의 Co₂O₃ 첨가는 액상의 점도를 낮추어 소결밀도를 감소시켰고, 이와 함께 경도값도 감소하였다. 산화코발트를 11 w t% 첨가하여 1350℃에서 소결할 경우, 3.86 g/㎤의 밀도와 12.32 GPa의 경도를 갖는 치밀한 소결체 제조가 가능하였다.

• 대한화학회지
• /
• 제38권9호
• /
• pp.695-700
• /
• 1994

여러가지 불균일 촉매$(Rh/Al_2O_3,\;Pd/C,\;Ni,\;Al_2O_3,\;Active\;carbon)$를 이용하여 CFC-113a의 가수소 분해반응을 액상과 기상에서 각각 조사하였다. 액상반응에서는 각 촉매에 따라 반응성은 차이가 났지만, 95% 이상의 높은 선택성으로 $HCFC-123(CF_3CHCl_2)$을 주었다. 특히 $Al_2O-3$가 액상반응에서 상당히 높은 반응성과 선택성을 보인 것은 주목할 만하다. 기상반응의 경우, 전이금속이 포함된 촉매(Pd/C, Pt/C)를 사용하였을 때에는 과수소화물인 $HCFC-133a(CF_3CH_2Cl)$와 HFC-143a(CF_3CH_3)$가 생성되었다. 한편, 액상반응에서 활성을 보이던 $Al_2O_3$는 기상반응에서는 거의 반응성을 보이지 않았다. $Al_2O_3$의 경우 용매로 THF를 사용하였을 경우에는 비교적 부반응 없이 깨끗하게 반응이 진행되었지만, MeOH를 사용하였을 때는 용매로 부터 $CH_3OCH_3$과 $CH_3CH_2OCH_3$ 등이 생성되면서 가수소 분해반응이 진행되었다. 따라서 액상반응에서는 용매의 역할이 중요한 것으로 해석하였다.

• Journal of Magnetics
• /
• 제15권2호
• /
• pp.61-63
• /
• 2010

We used $^1H$ nuclear magnetic resonance (NMR) to study the phase transitions and molecular dynamics in a characteristic ferroelectric liquid crystal with a carbon number n = 7, S-2-methylbutyl 4-n-heptyloxybiphenyl-4'-carboxylate (C7). The results were compared with those of our recent work on S-2-methylbutyl 4-n-octanoyloxybiphenyl-4'-carboxylate (C8), with a carbon number n = 8. While the recrystallization and isotropic phase transitions exhibited a first-order nature in the $^1H$ NMR spin-lattice and spin-spin relaxation measurements, a second-order nature was shown at the Sm-A - Sm-$C^*$ liquid crystalline phase transition. A soft-mode anomaly arising from the tilt angle amplitude fluctuation of the director, of which only a hint had been noticed in the C8 system, was manifested in the C7 system at this transition.

• 한국전기전자재료학회논문지
• /
• 제23권9호
• /
• pp.736-740
• /
• 2010

Nickel wires of 0.8 mm in diameter and 80 mm in length were electrically exploded in liquid media such as water, ethyl alcohol. The distribution of particle sizes was broad from a few micrometers to tens of nanometer. It was identified that the particles could be classified according to its sizes by using centrifugal separator. The powder prepared in distilled water showed mainly pure metallic Ni phase although a little oxide phase was observed. The powders prepared in ethyl alcohol showed complicated unknown phases, which is attributed to the compound of carbon in the organic liquid. This unknown phase was turned to pure metallic Ni phase after heat treatment.

• 한국응용과학기술학회지
• /
• 제19권4호
• /
• pp.251-257
• /
• 2002

Liquid-phase methanol synthesis via methyl formate using coal-derived syngas was carried out in a bench-scale(diameter 173 mm and dispersion height 1200 mm) slurry bubble column reactor(SBCR) Under the condition of $180^{\circ}$. 61 atm, 30 L/min, $H_{2}$/CO=2 and a slurry mixture of 2 kg of copper chromite and 0.5 kg of $KOCH_{3}$ suspended in 14 L of methanol, the per pass conversions of syngas is 6 %, maximum concentration of methyl formate 3.088 mol% and maximum synthesis, rate of methanol 0.8 gmole/kg ${\cdot}$ hr. It is a significant evidence that copper chromite powder as heterogeneous catalyst didn't active for the hydrogenolysis of methyl formate to methanol, resulting copper chromite powder was not efficiently suspended in a slurry mixture. To enhance the hydrogenolysis of methyl formate in liquid-phase methanol synthesis process, the designed SBCR have need to use the higher specific gravity solvent and/or decrease the catalyst particle size.

• 한국전기전자재료학회논문지
• /
• 제16권12호
• /
• pp.1131-1135
• /
• 2003

In the sintering of YIG, abnormal grain growth phenomena were observed. This abnormal grain growth is related to the sintering temperature in this experiment. In the sintering below 1450$^{\circ}C$, the sintered body showed narrow size distribution. However, in the sintering at 1450$^{\circ}C$, a few grains grew rapidly with respect to other grains, and bimodal size distribution was appeared. From the observation of the microstructure, liquid phase was not observed far from the abnormally grown large grains, but only near the large grains. This means that the abnormal grain growth was caused by the nonuniform distribution of liquid phase which promote the grains growth. Because the growth rate of grains near the liquid phase is much higher than that of the other grains, a few grains grow rapidly. This nonuniform distribution of liquid phase was thought to be due to the nonuniform mixing of the calcined powders. This abnormal grain growth was suppressed by enhancement of the compositional uniformity by multiple calcination.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제20권3호
• /
• pp.65-73
• /
• 2015

The hydrofluoric acid (HF) leakage accident occurred on September 2012 in Gumi, Korea affected the surrounding soils and plants. In this study, we investigated fluoride migration in Gumi area through geochemical properties of soil-liquid phase (pore water F and water-soluble F). The concentrations of porewater F and water-soluble F were obtained from N.D (Not detected) to 9.79 mg/L and from 0.001 to 21.4 mg/L, respectively. F in pore water seemed to be affected by artificial and natural origin, and PHREEQC results implied that fluorite is F control factor. F concentrations of soil and soil-liquid phase did not exceed concern level of regulatory criteria and showed similar trends compared by previous studies. Therefore, F contents remained in the soil and soil-liquid phase were considered to be not affected by HF leakage accident.

• 한국자동차공학회논문집
• /
• 제10권2호
• /
• pp.23-30
• /
• 2002

This present study experimentally investigates the behavior of liquid and vapor phase of fuel mixtures with changing the in-cylinder air motion in an optically accessible engine. The conventional MPI/DOHC engine was modified to gasoline direct injection engine with swirl motion. The images of liquid and vapor phases were captured in the motoring operation condition using exciplex fluorescence method. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution inside of cylinder respectively, In early injection timings $(BTDC\;270^{\circ},\;180^{\circ})$, tumble flow transported most of vapor phase to the lower region and the both sides of cylinder, so vapor phase didn't become uniform distribution up to the half of the compression stroke. In the case of swirl flow, the fuel mixture was confined near the swirl origin in upper region of cylinder. In late injection timings $(BTDC\;90^{\circ})$, tumble flow transported vapor phase to the intake valve and swirl flow to the exhaust valve.