알칼리 침전제에 의해 제조된 아연 중간생성물 및 산화아연 결정화

장대환,김보람,김대원,Jang, Dae-Hwan,Kim, Bo-Ram,Kim, Dae-Weon 한국결정성장학회 2021 韓國結晶成長學會誌 Vol.31 No.6

ZnO는 출발물질인 황산아연과 알칼리 침전제인 NaOH와 Na₂CO₃에 의해 생성된 아연 중간생성물의 변이 거동과 결정화 조건에 따라 제조하였다. ZnO 결정화를 위해 아연 중간생성물인 Zn₄(OH)₆SO₄·H₂O, Zn₅(OH)₆(CO₃)₂·H₂O를 각각 400℃, 800℃에서 1시간 하소하였고, 하소 온도는 열중량 분석을 기반으로 하였다. 아연 중간생성물인 Zn₄(OH)₆SO₄·H₂O은 400℃에서 Zn₄(OH)₆SO₄·H₂O, ZnO 결정상이 혼재됨을 확인하였고, 800℃에서 완전히 열분해되어 순수한 ZnO만 형성되었다. Na₂CO₃와 반응하여 생성된 아연 중간생성물인 Zn₅(OH)₆(CO₃)₂·H₂O는 400℃ 이상에서 완전한 ZnO의 결정상을 확인하였다. Na₂CO₃와 반응을 통해 상대적으로 낮은 하소 온도에서 나노 입자의 ZnO를 합성할 수 있었다. ZnO was synthesized according to the transformation behavior and crystallization conditions of Zn-intermediate obtained by zinc sulfate as a precursor and NaOH, Na₂CO₃ as a alkali agents. For ZnO crystallization, Zn₄(OH)₆SO₄·H₂O and Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate were calcined at 400℃ and 800℃ for 1 h, respectively, based on decomposition temperature from TGA. Zn₄(OH)₆SO₄·H₂O was confirmed to have mixed Zn₄(OH)₆SO₄·H₂O and ZnO at 400℃, and was completely thermally decomposed at 800℃ to form ZnO phase. The prepared Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate by the reaction with Na₂CO₃ was transformed to a complete ZnO crystallization over 400℃. Nano-sized ZnO can be synthesized at a relatively lower calcination temperature through the reaction with Na₂CO₃.

전기방사된 주석산화물 나노섬유의 공정 변수에 따른 직경 및 형상 제어 연구

장대환,이재은,좌용호,이영인,Jang, Dae-Hwan,Lee, Jae-Eun,Choa, Yong-Ho,Lee, Young-In 한국재료학회 2014 한국재료학회지 Vol.24 No.12

Diameter-controlled tin oxide nanofibers have been successfully prepared using electrospinning and a subsequent calcination process; their diameters, morphologies, and crystal structures have been characterized. The diameters of the as-spun nanofibers can be decreased by lowering the concentration of a polymer and a tin precursor in the electrospinning solution because of the decrease in the solution viscosity. The crystal structure of the nanofibers calcined at various temperatures from $200^{\circ}C$ to $800^{\circ}C$ has been proved to be the tetragonal rutile of tin oxide; crystallinity is improved by increasing the temperature. However, nanofibers with lower concentrations of tin precursor do not maintain their fibrous structures after calcination at high temperatures. In this study, the effect of the relationship between the precursor concentration and the calcination temperature on the diameter and the morphology of the tin oxide nanofiber has been systematically investigated and discussed.

폐내엽형 폐격리증

장대환 ( Dae Hwan Jang ),이현제 ( Hyun Je Lee ),한상호 ( Sang Ho Han ),박용준 ( Young Jun Park ),양승오 ( Seoung Oh Yang ),박용구 ( Young Koo Park ),김기호 ( Ki Ho Kim ) 대한결핵 및 호흡기학회 1988 Tuberculosis and Respiratory Diseases Vol.35 No.2

기후변화에 대응하는 공공하수도 관리의 중요성

장대환 ( Dae Hwan Jang ),오재일 ( Ja Ill Oh ),이수민 ( Su Min Lee ) 한국물환경학회(구 한국수질보전학회) 2011 공동 추계학술발표회 Vol.2011 No.-

코어-쉘 구조를 갖는 BaTiO₃@Fe 나노섬유의 합성 및 전자파 흡수 특성

이영인,장대환,성기훈,이규만,좌용호,Lee, Young-In,Jang, Dae-Hwan,Sung, Ki-Hoon,Lee, Kyuman,Choa, Yong-Ho 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.1

$BaTiO_3$-coated Fe nanofibers are synthesized via a three-step process. ${\alpha}-Fe_2O_3$ nanofibers with an average diameter of approximately 200 nm are first prepared using an electrospinning process followed by a calcination step. The $BaTiO_3$ coating layer on the nanofiber is formed by a sol-gel process, and a thermal reduction process is then applied to the core-shell nanofiber to selectively reduce the ${\alpha}-Fe_2O_3$ to Fe. The thickness of the $BaTiO_3$ shell is controlled by varying the reaction time. To evaluate the electromagnetic (EM) wave-absorbing abilities of the $BaTiO_3@Fe$ nanofiber, epoxy-based composites containing the nanofibers are fabricated. The composites show excellent EM wave absorption properties where the power loss increases to the high frequency region without any degradation. Our results demonstrate that the $BaTiO_3@Fe$ nanofibers obtained in this work are attractive candidates for electromagnetic wave absorption applications.

급속소결에 의해 제조된 Al₂O₃/Fe-Ni 나노복합재료의 미세조직 및 기계적 특성

이영인,이근재,장대환,양재교,좌용호,Lee, Young-In,Lee, Kun-Jae,Jang, Dae-Hwan,Yang, Jae-Kyo,Cho, Yong-Ho 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.3

A new High Frequency Induction Heating (HFIH) process has been developed to fabricate dense $Al_2O_3$ reinforced with Fe-Ni magnetic metal dispersion particles. The process is based on the reduction of metal oxide particles immediately prior to sintering. The synthesized $Al_2O_3$/Fe-Ni nanocomposite powders were formed directly from the selective reduction of metal oxide powders, such as NiO and $Fe_2O_3$. Dense $Al_2O_3$/Fe-Ni nanocomposite was fabricated using the HFIH method with an extremely high heating rate of $2000^{\circ}C/min$. Phase identification and microstructure of nanocomposite powders and sintered specimens were determined by X-ray diffraction and SEM and TEM, respectively. Vickers hardness experiment were performed to investigate the mechanical properties of the $Al_2O_3$/Fe-Ni nanocomposite.

유행성 출혈열의 역학적 조사

양철우 ( Chul Woo Yang ),장대환 ( Dae Hwan Jang ),조용호 ( Young Ho Cho ) 국군의무사령부 1992 대한군진의학학술지 Vol.23 No.1

철 샘플에 따른 구리 함유 폐에칭액의 시멘테이션 반응에 대한 연구

김보람(Bo-Ram Kim),장대환(Dae-Hwan Jang),김대원(Dae-Weon Kim) 한국청정기술학회 2021 청정기술 Vol.27 No.3

COF (Chip on film)용 폐에칭용액 내 구리가 약 3.5% 함유되어 있으며, 철 시편을 사용한 시멘테이션을 통해 구리를 회수하고자 하였다. 철 시편 3종류(플레이트, 칩, 분말)에 따른 시멘테이션 반응에 미치는 영향을 조사하였으며, 구리의 회수율을 높이고자 구리에 대한 철의 몰 비를 변수로 하였다. 반응 전・후 용액 내 시간에 따른 구리 농도의 변화를 확인하였으며, 몰 비를 증가시킬수록 초기 용액 내 구리 함량이 급격히 줄어드는 경향이 나타났다. 상온에서 1시간의 시멘테이션 반응 후 철 시편의 비표면적 값이 큰 플레이트, 칩, 분말 순으로 구리의 회수율이 증가하였다. 회수된 분말은 X선 회절 분석기(X-ray diffraction, XRD), 주사전자현미경(scanning electron microscopy, SEM) 및 에너지 분산형 분광분석법(Energy-dispersive X-ray spectroscopy, EDM) 분석을 통해 결정상과 결정 형태를 확인하였으며, 철 분말의 경우에는 회수된 구리 분말에 미반응된 철 성분이 혼재하였다. 구리에 대한 철의 몰 비 4의 조건으로 철 칩을 사용하였을 때, 구리 회수율 약 98.4%로 최적 조건으로 달성하였다. The waste etching solution for chip on film (COF) contained about 3.5% copper, and it was recovered through cementation using iron samples. The effect of cementation with plate, chip, and powder iron samples was investigated. The molar ratio (m/r) of iron to copper was used as a variable in order to increase the recovery rate of copper. As the molar ratio increased, the copper content in the solution rapidly decreased at the beginning of the cementation reaction. Before and after the reaction, the copper content of the solution was determined by Inductively Coupled Plasma (ICP) using copper concentration according to time. After cementation at room temperature for 1 hour, the recovery rate of copper had increased the most in the iron powder sample, having the largest specific surface area of the samples, followed by the chip and plate samples. The recovered copper powder was characterized for its crystalline phase, morphology, and elemental composition by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS), respectively. Copper and unreacted iron were present together in the iron powder samples. The optimum condition for recovering copper was obtained using iron chips with a molar ratio of iron to copper of 4 giving a recovery rate of about 98.4%.

초음파 분무 열분해법에 의한 산화물 환원 공정의 구형 Bi₂Te₃ 분말 합성

송철한(Chul-Han Song),장대환(Dae-Hwan Jang),진연호(Yun-Ho Jin),공만식(Man-Sik Kong) 한국표면공학회 2017 한국표면공학회지 Vol.50 No.2

Bismuth telluride (Bi₂Te₃) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic Bi₂Te₃ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical Bi₂Te₃ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above 375℃ for 6h. The reduced Bi₂Te₃ powders have a mean particle size of 1.5 μm. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

신증후출혈열의 역학적 조사: 1985~1990

양철우 ( Yang Cheol U ),장대환 ( Jang Dae Hwan ),조영호 ( Jo Yeong Ho ),방병기 ( Bang Byeong Gi ),이호왕 ( Lee Ho Wang ) 대한내과학회 1992 대한내과학회지 Vol.42 No.6

연구배경 : 최근 한국군내에서의 신중후출혈열의 발생 양상을 알아보기 위하여 역학조사를 시행하였다. 방법 : 1985년 1월부터 1990년 12월까지 국군수도병원에 입원하여 신중후출헐열로 화진된 748명을 대상으로 연간 환자수, 사망자수, 소유행시기, 발병후 입원시까지의 기간, 호발지역 및 비호발지역, 지역별환자수, 사망원인 및 시기를 조사하였다. 결과 : 1) 입원환자수는 연평균 124명이었으며 최근 3년간은 연평균 약 90명으로 급격한 감소를 보였으며 6년간 총 사망자수는 21명으로 연평균 2.8%였다. 2) 소유행시기(5~7월)는 감소하는 추세를 보였다(전체 환자수의 9.2%). 3) 전체 환자수의 7.6%만이 발병 1~3병일째 후송되었다. 4) 지역별 환자발생수는 호발지역에 국한되는 양상을 보였고(경기 65%, 강원 33%)비호발지역은 전체 환자수의 약 2%에 불과하였다. 5) 호발지역의 확산이나 남하하는 경향은 없었다. 6) 경기지역내 호발지역은 파주(153명, 32%), 연천(99명, 20%)으로 전체 환자발생수의 대부분을 차지하였고 강원지역에서는 철원이 가장 많았으며(125명, 50%)이외에 화전, 인제, 양구, 고성순이었다. 7) 주된 사망원인은 비가역성 쇽(48%), 폐출혈(14%), 뇌병중(14%)으로 비가역적 쇽으로 인한 사망이 가장 높았다. 8) 주된 사망시기는 저혈압기였으나(11예, 52%) 그 비율은 감소하였다. 9) 유행형보다 산발형에서, 대유행기보다 소유행기에서 사망율이 높았다. 결론 : 이상의 결과에서 신중후출혈열의 발병율과 사망율은 최근에 감소추세에 있다고 사료되나 매년 100여명의 환자가 지속적으로 발생하고 있음을 알 수 있었다. 향후 신중후출혈열백신의 보급이 신중후출혈열의 발생율, 사망율 및 임상양상에 어떠한 영향을 줄 것인지에 대한 지속적인 연구가 있어야 할 것이다. BackgroundTo investigate the recent epidemiologic changes of HFRS in Korean Military. Methods:We reviewed th 748 cases of HFRS who admitted to Central Armed Forces General Hospital during 1985- 1990 and evaluated the incidence, death rate, interval from onset to admission, endemic season, prevalent area, cause of death, and phase of death. Results: 1) The number of HFRS patients and death rates have decreased about 124 per year, 2.8 percent per year, respectively. 2) Two endemic seasons for HFRS were now changed into monopeak from October to December. 3) Only 7.6 percent of HFRS patients had been transferred to our hospital within the 3rd day of illness onset. 4) Almost all of the patients occurred in two provinces (Kyunggido and Kangwondo) with only 2 percent of the patients occurring in other provinces and the incidence in Kyunggido affected overall incidence of HFRS. 5) There was little change in the distribution of endemic areas and there was little evidence of spread to the other provinces. 6) HFRS patients in Paju and Yeonchon comprised more than half of all cases in Kyunggido and the most endemic area in Kangwondo was Cholwon, and other areas were Hwachon, Inje, Yanggu, Kosung, in that order. 7) More than half of the fatal cases occurred during the hypotensive stage but its proportion has decreased. 8) Causes of death were primary shock (48%), cerebrovascular accident (14%), pulmonary hemorrhage (14%), DIC (lo%), respiratory failure (lo%), sepsis (5%), in that order. 9) The sporadic from of HFRS had a higher mortality than endemic forms. Conclusion: It seems that incidence and death rate have decreased, however, the possibility and ourbreak or periodicity cannot be ruled out and further evaluation of incidence and severity in HFRS will be necessary with the clinical trial of HFRS vaccine.