메탄에 의한 Ag/Al₂O₃ 촉매의 선택적 탈질 환원촉매반응에서 탈질전환율에 미치는 황화물 형성의 영향과 Mg첨가 효과

최희락,유창용,하헌필,Choi, Hee-Lack,Yu, Chang-Yong,Ha, Heon-Phil 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.2

The influence of sulfate on the selective catalytic reduction of $NO_x$ on the Ag/$Al_2O_3$ catalyst was studied when $CH_4$ was used as a reducing agent. Various preparation methods influenced differently on the $deNO_x$ activity. Among the methods, cogelation precipitation gave best activity. When sulfates were formed on the surfaces of samples prepared by impregnated and deposition precipitation, $deNO_x$ activity was enhanced as long as suitable forming condition is satisfied. The major sulfate formed in Ag/$Al_2O_3$ catalyst was the aluminum sulfate and it seems that this sulfate acted as a promoter. When Mg was added to the Ag/$Al_2O_3$ catalyst it promoted $deNO_x$ activity at high temperature. Intentionally added sulfate also enhanced $deNO_x$ activity, when their amount was confined less than 3 wt%.

Pb₂C₂O₄(NO₃)₂ㆍ2H₂O의 제조 및 특성평가

최희락(Hee-Lack Choi) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.1

On the precipitation and ripening reaction of the precipitates from a lead nitrate and an oxalic acid dissolved in ethanol, a new crystalline phase was obtained, whose X-ray diffraction data have not previously been reported. The crystal system was determined to be monoclinic. The unit-cell parameters were refined to a =10.613(2)Å, b =7.947(2)Å, c =6.189(1)Å, and β =104.48(2)°.

Ti₂O₂(C₂O₄)(OH)₂ㆍH₂O의 제조 및 특성평가

최희락(Hee-Lack Choi) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.1

During studies of the ripening reaction of titanium oxalate, a new crystalline phase has been found. The crystal system was determined to be orthormbic with space group C222₁. The unit cell parameters were refined to a=10.503(2)Å b=15.509(3)Å c=9.700(1)Å. The chemical formula of the crystal Ti₂O₂(C₂O₄)(OH)₂ㆍH₂O. When heated to temperatures between 310℃ and 380℃, the material became amorphous. Heated above 410℃ converted it into the anatase-type titanium dioxide.

수산에타놀법에 의한 PbTiO₃분말의 합성

최희락(HEE-LACK CHOI),이봉(BONG LEE),문창권(CHANG-KWAN MOON) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.1

PbTiO₃ was prepared by addition of lead-thanium mixed aqueous solution to an ethanol solution of oxalic acid. The influence of various ripening factors was investigated. On the basis of the results in the mono-component system, we studied the foramtion of PbTiO₃ phase with various ripening conditions. The PbTi₃ phase formation was accelerated with the ripening time, temperature and uhrasonic irradiation.

사지에 발생한 혈관종의 수술적 치료 후 재발에 대한 분석

김영신,최희락,이준모,이형석,김정렬,Kim, Young-Sin,Choi, Hee-Lack,Lee, Jun-Mo,Lee, Hyung-Seok,Kim, Jung-Ryul 대한근골격종양학회 2010 대한골관절종양학회지 Vol.16 No.2

목적: 사지에 발생한 혈관종의 수술적 치료 후 재발에 대한 위험인자를 분석하고 체간에 발생한 경우와 비교분석 하고자 하였다. 대상 및 방법: 1998년 7월부터 2009년 9월까지 본원에서 사지의 혈관종을 치료받은 120예를 대상으로 하였고 같은 기간 체간에 발생하여 수술적 치료를 시행한 53예를 비교 군으로 하였다. 종양의 호발연령, 발생부위, 위치, 크기, 조직학적 형태를 분석하였고 로지스틱 회귀 분석을 통해 각각의 인자와 재발과의 상관관계를 분석하였다. 결과: 재발율은 사지에서 11.7%였고, 체간에서 9.4%였다. 재발의 위험 인자 중 호발 연령, 위치, 크기, 조직학적 형태에 따른 통계학적 의의는 없었다. 그러나 발생 부위가 통계학적으로 의미있는 결과를 보였으며(p=0.058), 특히 사지에서는 수부, 전완부, 족부등 말단부, 체간에서는 두경부에서 호발하였다. 결론: 사지에 발생한 혈관종에 대한 재발은 수부, 전완부, 족부와 같이 완전 절제가 어려운 부위에서 흔히 발생하였다. 따라서 혈관종의 수술적 치료시 완전절제가 이루어 지지 않았을 경우는 재발에 대한 주의 깊은 추시가 요구된다. Purpose: To analyse the risk factors for recurrence of hemangiomas in extremities after surgical treatment and to compare with those of trunk. Materials and Methods: 120 cases of hemangioma with surgical treatments from June 1998 to September 2009 were analysed. 53 cases with surgical treatment on trunk in the same period were set to be the control group. We analyze several factors: age, location, site, size, histologic types and correlation between recurrence and each risk factor using logistic regression analysis. Results: Recurrence rate was 11.7% in extremities and 9.4% in trunk. There were no correlation between recurrence and age, site, size, histologic type. But, there was stastically significant correlation between recurrence rate and location, especially hand, forearm, feet in extremities and head and neck in trunk. Conclusion: Recurrence after surgical treatment of hemangioma is highly prevalent in anatomical location such as, hand, foot and forearm those are difficult to achieve complete resection because of close to neurovascular structures. Careful observation should be needed owing to incomplete resection can occurs recurrence.

광전도성 고분자와 안트라센 유도체를 이용한 백색 전계발광소자의 발광 특성

이정환,최희락,이봉,Lee Jeong-Hwan,Choi Hee-Lack,Lee Bong 한국재료학회 2005 한국재료학회지 Vol.15 No.8

Organic electroluminescence devices were made from 1,4-bis-(9-anthrylvinyl)benzene (AVB) and 1,4-bis-(9-aminoanthryl)benzene (AAB) anthracene derivatives. Device structure was ITO/AVB/PANI(EB)/Al (multi-layer device) and ITO/AAB:DCM/Al(single-layer device). In these devices, AVB, polyaniline(emeraldine base) (PANI(EB)) and AAB were used as the emitting material. 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H -pyran(DCM) was used as red fluorescent dopant. We studied change of fluorescence wavelength with concentration of DCM doped in AAB. The ionization potential (IP) and optical band gap (Eg) were measured by cyclic voltammetry and UV-visible spectrum. We compared with difference of emitting wavelength between photoluminescence and electroluminescence spectrum. In case of the multi-layer device, PANI and AVB EL spectra have similar wave pattern to each PL spectrum and when PAM and AVB were used at the same time, and multi-layer device showed that a balanced recombination and radiation kom PANI and AVB. In case of the single-layer device, with the increase of DCM concentration, the blue emission decreases and red emission increases. This indicates that DCM was excited by the energy transfer from AAB to DCM or the direct recombination at the dopant sites due to carrier trapping, or both. The device with $1.0wt\%$ DCM concentration gave white light.

V₂O₅/TiO₂ 촉매의 선택적 환원촉매반응에서 격자산소의 역할

하헌필,최희락,Ha, Heon-Phil,Choi, Hee-Lack 한국재료학회 2006 한국재료학회지 Vol.16 No.5

In situ electrical conductivity measurements on $V_2O_5WO_3/TiO_2$ catalysts were carried out at between 100 and $300^{\circ}C$ under pure oxygen, NO and $NH_3$ to investigate the reaction mechanism for ammonia SCR (selective catalytic reduction) de NOX. The electrical conductivity of catalysts changed irregularly with supply of NO. It was, however, found that the electrical conductivity change with ammonia supply was regular and the increase of electrical conductivity was mainly caused by reduction of the labile surface oxygen. The electrical conductivity change of catalysts showed close relationship with the conversion rate of NOx. Variation of conversion rate in atmosphere without gaseous oxygen also showed that labile lattice oxygen is indispensable in the initial stage of the de NOx reaction. These results suggest that liable lattice oxygen acts decisive role in the de NOx mechanism. They also support that de NOx reaction occurs through the Eley?Rideal type mechanism. The amount of labile oxygen can be estimated from the measurement of electrical conductivity change for catalysts with ammonia supply. This suggests that measurement of the change can be used as a measure of the de NOx performance.

탄산리튬 분말 제조에 있어서 초음파 에너지를 적용한 기액반응에 관한 연구

김대원,김보람,최희락,Kim, Dae-Weon,Kim, Bo-Ram,Choi, Hee-Lack 한국결정성장학회 2020 한국결정성장학회지 Vol.30 No.2

In the previous study, we reported the result to prepare lithium carbonate powder from various lithium-contained solution. Therefore, using the lithium hydroxide solution, it is conformed that the reaction could occur thermodynamically, and the recovery rate of lithium was 89.4 %. In this study, we carried out the experiment to prepare lithium carbonate powder through gas-liquid reactions with lithium hydroxide solution and CO₂ gas using ultrasound energy. In case ultrasonic energy is applied to the reaction of lithium carbonate, the recovery rate of lithium at room temperature was approximately 83.8 %, and the recovery rate of lithium was greatly increased to approximately 99.9 % at 60℃ reaction temperature. And when ultrasonic energy is not applied, the particle size of lithium carbonate powder was 7.7 ㎛ in D50. But the particle size of lithium carbonate powder was significantly reduced to 8.4 ㎛ in D50 under the influence of ultrasonic. 기존 연구에서 본 연구자들은 여러 가지 리튬 함유 용액으로부터 탄산리튬 분말 제조에 대하여 보고하였으며, 이중에서 수산화리튬 용액과 CO₂ 가스와의 반응이 열역학적으로 탄산리튬 생성이 가능하고 89.4 %의 회수율을 나타내었다. 본 연구에서는 수산화리튬 용액과 CO₂ 가스와 기액반응에 있어서 초음파에너지를 가하여 탄산리튬 분말을 제조하는 실험을 실시하였다. 실온에서 탄산리튬 생성 반응에 초음파를 가하였을 경우에 리튬의 회수율은 83.8 %이었으며, 60℃에서 초음파를 가하면 99.9 %로 회수율이 급격하게 증가되었다. 또한 초음파 에너지를 가하지 않을 경우의 입자 크기는 D50에서 약 87.7 ㎛이었으며, 초음파를 가한 경우에는 D50이 약 8.4 ㎛로 급격하게 감소하는 결과를 얻었다.

평판형 나트륨 유황 전지의 초기 충방전시 방전전압 변화

김성인,김헌태,최희락,임산수대,양기덕,범진형,김창삼,Kim, Seong-In,Kim, Heon-Tae,Choi, Hee-Lack,Lim, San-Su-Dae,Yang, Kee-Deok,Beum, Jin-Hyung,Kim, Chang-Sam 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.4

나트륨 유황 전지는 $350^{\circ}C$ 이상의 고온에서 작동하는 대용량 전지로 에너지 저장 시스템에 주로 사용된다. 전지는 음극 액체 나트륨과 양극 액체 유황 그리고 고체 전해질 베타 알루미나(${\beta}^{{\prime}{\prime}}$-alumina)로 구성되어 있다. 이 전지는 초기충방전 사이클에서 상당한 전압변화를 보이기 때문에 전지의 안정화를 위해 컨디셔닝 과정이 필요하다. 실험 결과 전지 전압 변화의 주요한 원인 중의 하나가 액체 나트륨과 고체 전해질과의 접촉 면적이 변하기 때문인 것을 알았다. The sodium-sulfur batteries which operate at $350^{\circ}C$ have been mainly used in the field of energy storage system. This batteries consist of liquid sodium anode, sulfur cathode and ${\beta}^{{\prime}{\prime}}$-alumina solid electrolyte. The conditioning process for stabilization of the batteries is essential since the cells show considerable fluctuation of discharge voltage at the beginning of discharge/charge cycles. It is found that one of the reasons of the fluctuation is the gradual change of contact area between molten sodium and solid electrolyte.

Na-ZnCl₂ 전지에서 Zn/NaCl 비율이 충방전 특성에 미치는 영향

김헌태,김성인,최희락,박원일,김창삼,Kim, Heon-Tae,Kim, Seong-In,Choi, Hee-Lack,Park, Won-Il,Kim, Chang-Sam 한국결정성장학회 2015 韓國結晶成長學會誌 Vol.25 No.2

고체전해질을 사용하는 $Na-NiCl_2$ 전지와 같은 원리로 작동하는 $Na-ZnCl_2$ 전지는 $Na-NiCl_2$ 전지에 비하여 재료비용을 40 % 절감할 수 있다. $Na-ZnCl_2$ 전지는 충전과정에서 Zn과 NaCl이 반응하여 직접 $ZnCl_2$가 생성되는 것이 아니라, 중간생성물인 $Na_2ZnCl_4$를 거쳐서 $ZnCl_2$이 되기 때문에, 출력 전압이 다른 4개의 구간으로 분리되어 1.92~2.13 V 범위의 전압을 갖는 것으로 알려져 있다. 충전과정에서 Zn과 NaCl이 반응하여 직접 $ZnCl_2$가 생성되는 것이 아니라, 중간생성물인 $Na_2ZnCl_4$를 거쳐서 $ZnCl_2$이 된다. 그로인해 출력 전압이 다른 4개의 구간으로 분리되어 1.92~2.13 V 범위의 전압을 갖는 것으로 알려져 있다. 그러나 전지 특성에 영향을 미치는 양극 조성, 충방전 심도 및 첨가제 등에 대해서는 알려져 있지 않다. 여기서는 $Na-ZnCl_2$ 전지에서 양극으로 사용되는 Zn과 NaCl의 비율을 변화시키면서 양극의 조성비가 전지의 충방전 특성에 미치는 영향을 조사하여, Zn/NaCl 최적 비율이 1.3~1.7 범위에 있음을 알았다. $Na-ZnCl_2$ battery, which operates as the same mechanism of $Na-NiCl_2$ battery using solid-electrolyte, is able to reduce its material cost by 40 % comparing to the $Na-NiCl_2$ battery. It has been known that the $Na-ZnCl_2$ battery produces $Na_2ZnCl_4$ as an intermediate phase during charge/discharge process. Therefore, the redox process is divided into four steps having the voltage range of 1.92~2.13 V. However, effects of the critical factors such as the composition of cathode materials, depth of charge and discharge, and additives have not been reported yet. We examined the effect of the Zn/NaCl ratios and revealed that its optimum ratio was in the range of 1.3~1.7.