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Propylene Oxide를 이용한 졸-겔법에 의한 MO·Fe<sub>12</sub>O<sub>18</sub> (M/Ba, Sr) 나노 분말의 합성과 물리적 특성
이수진,최석범,곽형섭,백승욱,Lee, Su Jin,Choe, Seok Burm,Gwak, Hyung Sub,Paik, Seunguk 한국공업화학회 2006 공업화학 Vol.17 No.4
Propylene oxide (PPO)를 gelation agent로 한 졸-겔법으로 입자가 균일하고 자기적 특성이 우수한 $MO{\cdot}Fe_{12}O_{18}$ (M/Ba and Sr)의 구조식을 가지는 M-type hexagonal ferrite를 제조하였다. 본 방법으로 얻은 졸-겔용액은 매우 안정적인 분산상태를 보이며, $Fe^{3+}$의 겔화가 진행되고, 생성된 $Fe_2O_3$의 표면에서 $Ba^{2+}$ 또는 $Sr^{2+}$의 겔화가 진행되는 것으로 설명될 수 있어서, +3가 이하의 금속이라도 +3가 이상의 금속 존재 하에는 겔화가 가능한 것을 확인하였다. 또한, 기존 방법과 비교하여 값싼 원료를 사용하며, 반응 시간도 1 min 이내로 짧아지는 장점이 있다. 본 제조법으로 얻어진 분말은 기왕에 발표된 문헌 값과 비교하면 $150^{\circ}C$ 이상 낮은 열처리 온도에서 최고의 자기적 특성을 나타냈으며, 향상된 자기적 특성을 보였다. Sr-ferrite의 경우 최대포화자화 값 74.4 emu/g, 보자력 값 6198 Oe을, Ba-ferrite의 경우도 최대포화자화 값 68.1 emu/g, 보자력 값 5155 Oe을 보였다. 이들은 기존에 발표된 문헌 값과 비교하면 각각 10%와 5% 이상 증가된 보자력 값을 나타내어, 고밀도 자기기록재료에 적합함을 확인하였다. 제조된 분말은 1차 건조 분말의 경우 3~5 nm의 입자들이 응집된 50 nm 정도의 구형입자가 생성되고, 열처리 후에는 500 nm 정도의 고른 크기를 가진 육각판상형 입자가 생성된다. Nano sized mixed metal hexagonal ferrite powders with improved magnetic properties have been prepared by sol-gel method using propylene oxide as a gelation agent. To obtain the desired ferrite, two different metal ions were used. One of the ions has only +2 formal charge. The key step in the processes is that hydrated $Ba^{2+}$ or $Sr^{2+}$ ions are hydrolyzed and condensed at the surface of the previously formed $Fe_{2}O_{3}$ gel. In this processes, all the reaction can be finished within a few minutes. The magnetic properties of the produced powder were improved by heat treatment. The highest values of the magnetic properties were achieved at temperature $150^{\circ}C$ lower than those of the previously published values. The highest observed values of coercivity and the saturation magnetization of Sr-ferrite and Ba-ferrite powder were 6198 Oe, 5155 Oe and 74.4 emu/g, 68.1 emu/g, respectively. The ferrite powder annealed at $700^{\circ}C$ showed spherical particle shapes. The resulting spheres which were formed by the aggregation of nanoparticles with size 3~5 nm have diameter around 50 nm. The powder treated at $800^{\circ}C$ showed hexagonal-shaped grains with crystallite size above 500 nm.
이천수,윤무홍,최석범,노승백 ( Chun Soo Lee,Mu Hong Yoon,Seok Burm Choe,Seung Baik Rho ) 한국공업화학회 1992 공업화학 Vol.3 No.1
수용액에서 amine류와 arylsulfonyl carbamate류를 반응시켜 다음과 같은 arylsulfonyl urea유도체들을 좋은 수율로 쉽게 합성할 수 있다 : 1) N-Arylsulfonyl-N`-arylurea 유도체, 2) N-Arylsulfonyl-N`-alkyl urea 유도체, 3) N-Arylsulfonyl-N`-heterocyclic urea 유도체. Arylsulfonyl urea의 합성에 관한 반응메카니즘은, 먼저 산-염기 반응에 의해 ion-pair형태가 만들어지고, 그 다음 사면체형 중간체를 형성하는 친핵성첨가반응, 그리고 산촉매애 의한 alkoxide ion 과 양성자의 제거반응에 따라 일어난다. Arylsulfonyl urea derivatives can be easily prepared in good yield by treating amines with arylsulfonyl carbamates in aqueous solution : 1) N-Arylsulfonyl-N`-aryl urea derivatives, 2) N-Arylsulfony-N`-alkyl urea derivatives, 3) N-Arylsulfonyl-N`-heterocyclic urea derivatives. The proposed reaction mechanisms for preparing arylsulfonyl ureas involve formation of an ion-pair conformation by initial acid-base reaction, then formation of a so-called tetrahedral intermediate by nucleophilic addition, followed by an acid-catalyzed elimination of an alkoxide ion and loss of a proton.
超音波의 化學的 效果 : Principles and applications 原理와 應用
崔錫範 啓明大學校 産業技術硏究所 1992 産業技術硏究所 論文報告集 Vol.15 No.1
The chemical effects of ultrasound were surveyed. The principles of the cavitation phenomenon and its physical properties were discussed. Also it is shown that the chemical effects of cavitation in homogeneous media and heterogeneous media are quite different. thou the origin of the cavitation is the same. Possible applications of ultrasound in industry in future also were commented.
崔錫範 啓明大學校 産業技術硏究所 1992 産業技術硏究所 論文報告集 Vol.15 No.1
New synthetic route for the synthesis of (ηb-toluene)Ni(SiCl₃)₂ using diethyl ether-toluene exchange reaction was developed. Also new nickel-acetonitrile complexes having molecular formular Ni(CH₃CN)₂L₂(L=SiCl₃, SiF₃) were prepared by toluene-acetonitrile ligand exchange reactions. The new complexes are very sensitive to air but have relatively good thermal stability.
에틸렌 중합 반응에 대한 닉켈-알루미늄 혼합 촉매계에서의 알루미늄 화합물에 의한 촉매특성에 관한 연구
최석범 啓明大學校 産業技術硏究所 1993 産業技術硏究所 論文報告集 Vol.16 No.2
A new catalytic system for ethylene oligmerization reaction was developed. Ni(SiCl₃)₂(PEt₃)₂ and AlEtCl₂ were used as catalysts. The role of nickel and aluminum compunds on the catalytic reaction were examined. The major role of the aluminum compound on the ethylene oligonerization reaction seems to made ethylene attack the nickel center easily decreasing the electron density on the nickel atom while the nickel compound do its role as the catalyst precursor. Also a mechanistic routes for the generation of the active species was proposed.