Titanium n-propoxide의 가수분해에 의한 분말 합성과 반응 메커니즘

명중재,박진구,경진범,김호건 한국분말야금학회 1996 한국분말야금학회 학술대회논문집 Vol.1996 No.1

졸-겔법에 의한 TiO₂ 미분말 합성과 반응메카니즘(I): Titanium isopropoxide의 가수분해

명중재,정용선,경진범,김호건,Myung, Jung-Jae,Chung, Yong-Sun,Kyong, Jin-Bum,Kim, Ho-Kun 한국공업화학회 1996 공업화학 Vol.7 No.4

$TiO_2$ fine powders were synthesized via hydrolysis reaction of titanium isopropoxide in isopropanol solvent and the reaction rates were studied by use of UV spectroscopic method. The reactions were controlled to proceed to pseudo-first-order reaction in the presence of excess water in isopropanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reactions using $D_2O$ were also carried out to determine the catalytic character of water. n value of water molecules in transition state and the thermodynamic parameters showed that the reaction proceeded by $S_N2$ mechanism. $TiO_2$ powders synthesized in this reaction were almost spheric forms and had average particle size of $0.3{\mu}m$ diameter. Isopropanol 용매 내에서 titanium isopropoxide($Ti(O-^iPr)_4$)의 가수분해반응에 의하여 $TiO_2$ 미분말을 합성하였고 가수분해 반응 속도를 자외선분광법에 의하여 측정하였다. 반응은 $Ti(O-^iPr)_4$의 농도에 비하여 물 농도를 크게 하여 유사일차반응으로 진행시켰고, 물 농도 및 온도의 변화에 따른 반응속도상수를 Guggenheim method로 계산하였다. 또한 물의 동위원소 효과를 측정하여 반응에 참여하는 물분자의 촉매성을 확인하였다. 입도분석과 미세구조 관찰 결과, 얻어진 $TiO_2$ 미분말은 $0.3{\mu}m$정도의 입자크기를 갖는 구형의 입자로 확인되었다. 또한 반응속도로부터 전이상태에 참여하는 n value와 열역학적 파라메타를 계산한 결과, $Ti(O-^iPr)_4$의 가수분해반응은 이분자 반응인 $S_N2$ mechanism으로 진행하는 것으로 추정되었다.

졸 - 겔법에 의한 TiO2 미분말 합성과 반응메카니즘 (Ⅰ) : Titanium isopropoxide 의 가수분해

명중재,정용선,경진범,김호건 ( Jung Jae Myung,Yong Sun Chung,Jin Bum Kyong,Ho Kun Kim ) 한국공업화학회 1996 공업화학 Vol.7 No.4

Isopropanol 용매 내에서 titanium isopropoxide(Ti(O-^iPr)₄)의 가수분해반응에 의하여 TiO₂미분말을 합성하였고 가수분해 반응 속도를 자외선분광법에 의하여 측정하였다. 반응은 (Ti(O-^iPr)₄)의 농도에 비하여 물 농도를 크게 하여 유사일차반응으로 진행시켰고, 물 농도 및 온도의 변화에 따른 반응속도상수를 Guggenheim method로 계산하였다. 또한 물의 동위원소 효과를 측정하여 반응에 참여하는 물분자의 촉매성을 확인하였다. 입도분석과 미세구조 관찰 결과, 얻어진 TiO₂미분말은 0.3μm정도의 입자크기를 갖는 구형의 입자로 확인되었다. 또한 반응속도로부터 전이상태에 참여하는 n value와 열역학적 파라메타를 계산한 결과, (Ti(O-^iPr)₄)의 가수분해반응은 이분자 반응인 S_n2 mechanism으로 진행하는 것으로 추정 되었다. TiO₂fine powders were synthesized via hydrolysis reaction of titanium isopropoxide in isopropanol solvent and the reaction rates were studied by use of UV spectroscopic method. The reactions were controlled to proceed to pseudo-first-order reaction in the presence of excess water in isopropanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reactions using D₂O were also carried out to determine the catalytic character of water. n value of water molecules in transition state and the thermodynamic parameters showed that the reaction proceeded by S_n2 mechanism. TiO₂powders synthesized in this reaction were almost spheric forms and had average particle size of 0.3μm diameter.

결정화 소결에 의한 생체활성재료의 제조

명중재,이안배,정용선,신건철,김호건 한국결정성장학회 1998 한국결정성장학회지 Vol.8 No.1

CaO-$SiO_2-P_2O_5$ 3성분계 유리화 영역(glass forning region)내의 여러조성(A:$SiO_2$- rich조성, B:CaO-rich조성, C:$P_2O_5$-rich조성, D, E:A, B, C의 중간조성)을 가지는 유리분말을 결정화시켰을 때 유리중에 석출되는 결정상(crystal phase)을 분말 XRD로 확인하였다. 여러조성중 apatite(($Ca_{10}(PO_4)_6O$)와 $\beta$-wollastonite($CaSiO_3$)결정이 석출되고, 굽힘강도가 우수한 E조성(CaO 49.4, $SiO_2\;36.8,\;P_2O_5$8.8wt%)을 선택하여 이 조성의 유리분말을 일방향으로 결정화 소결하였다. 제조된 결정화 소결체에 대하여 charaterization을 하고 굽힘강도를 측정하였다. 또한 결정화 소결체와 생체뼈와의 결합성을 조사하기 위하여 유사체액(simulated body fluid)내에서 침적실험을 하였으며, 결정화 소결체의 표면을 thin-film XRD, FT-IR로 분석하였다. 실험결과, apatite와 wollastonite 결정이 석출된 치밀한 결정화 소결체가 얻어졌으며, 이들 결정은 wollastonite 결정의 (202)면이 인상방향에 수직으로 성장하는 경향을 보였다. 또한 제조된 결정화 소결체는 평균 186.9MPa의 굽힘강도를 나타내어 일반적 방법으로 제조되는 결정화 소결체보다 높은 역학적 성질을 보였다. 유사체액내의 침적실험결과, 시료표면위에 apatite 결정층이 3일후부터 형성되어 생체뼈와 화학결합을 이룰 가능성이 있음을 알았다. The crystal phases precipitated in various compositions glass of CaO-$SiO_2-P_2O_5$ system, were identified by XRD. E composition (CaO 49.4, $SiO_2\;36.8,\;P_2O_5$ 8.8 wt%) glass in which both apatite(($Ca_{10}(PO_4)_6O$ and $\beta$-wollastonite($CaSiO_3$) crystals would precipitate by heating, was selected as an experimental composition to prepare the glass ceramics with high bending strength and good bioactivity to the living bone. Glass powders of E composition were unidirectionally crystallized at $1050^{\circ}$C in the temperature-gadient furnace and the resultant glass ceramics were characterized. Bending strength of the glass ceramics was also measured. To investigate the bond forming ability between the glass ceramics and living bone tissue, soaking test of glass ceramics in simulated body fluid was carried out. Densed glass ceramics composed of apatite and $\beta$-wollastonite crystal were prepared by unidirectional crystallization under the optimum conditions. (2 0 2) plane of $\beta$-wollastonite crystals tended to grow perpendicularly to the crystallization direction. Average bending strength of this glass ceramics was 186.9 MPa, higher than that of the glass ceramics prepared by isothermal (not directional) crystallization In soaking test, a thin layer of apatite crystallite was formed on surface of the glass ceramics in 3 days. Apatite crystals formed on the glass ceramics could be act a role to make the chemical bond between the glass ceramics and living bone tissue.

연구논문 - 무기 / 촉매 : Titanium isopropoxide 의 가수분해에 대한 속도론적 연구

명중재,김호건,경진범 한국공업화학회 1995 한국공업화학회 연구논문 초록집 Vol.1994 No.1

졸 - 겔법에 의한 TiO2 미분말 합성과 반응메카니즘 (Ⅱ) : Titanium n - propoxide 의 가수 분해

명중재,박진구,정용선,경진범,김호건 ( Jung Jae Myung,Jin koo Park,Yong Sun Chung,Jin Bum Kyong,Ho Kun Kim ) 한국공업화학회 1997 공업화학 Vol.8 No.5

n-propanol 용매내에서 titanium n-propoxide(Ti(O^nPr)₄)의 가수분해반응에 의하여 TiO₂미분말을 합성하였고, 가수분해속도를 자외선 분광법에 의하여 측정하였다. 분말합성은 water/alkoxide의 농도비가 약 300정도에서 실시하였으며, 물농도, 반응온도, 반응시간 및 반응용액의 산 ·염기효과에 의한 합성조건을 조사하였다. 반응은 Ti(O^nPr)₄의 농도에 비하여 물농도를 과량으로 하여 유사일차반응으로 진행시켰고, 반응속도상수를 Guggenheim method로 계산하였다. 또한 물의 동위원소효과(D₂O)를 측정하여 반응에 관여하는 물분자의 촉매성을 확인하였다. 실험결과 중성 및 염기성 용액 조건에서 TiO₂미분말이 합성되었고, 미세구조 관찰로부터 TiO₂입자는 직경 0.4-0.7㎛정도의 구형입자로 확인되었으며, 물의 농도와 반응온도가 증가할수록, 반응시간이 감소할수록 입자크기는 작아지는 경향을 보였다. 물의 동위원소효과로부터, 물분자는 nucleophilic catalysis로 작용하고 있으며, 반응속도로부터 전이상태에 참여하는 n-value와 열역학적 파라미터를 계산한 결과, Ti(O^nPr)₄의 가수분해반응은 이분자 반응인 associative S_N2 mechanism으로 진행하는 것으로 추정되었다. TiO₂ powders were synthesized via hydrolysis reaction of titanium n-propoxide in n-propanol solvent and the reaction rates were studied by use of UV-vis spectroscopic method. Concentration of water, reaction temperature, reaction time and acid-base effects of the solution were investigated to determine the optimum conditions for TiO₂ powder synthesis. The reaction were controlled to proceed to pseudo-first order reaction in the presence of excess water in n-propanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reaction using D₂O was also carried out to determine the catalytic character of water. TiO₂ powders were synthesized only in the neutral and basic solution and those were almost spheric forms having average particle size of 0.4-0.7㎛ diameter. Particle size decreased with increasing concentration of water and reaction temperature, however, increased with increasing reaction time. Associative S_N2 mechanism for the hydrolysiswas proposed from the data of n-value in the transition state and thermodynamic parameter. D₂O solvent isotope effect showed that H₂O molecules reacted as nucleophilic catalysis.

졸-겔법에 의한 TiO₂미분말 합성과 반응메카니즘(II): Titanium n-propoxide의 가수분해

명중재,박진구,정용선,경진범,김호건,Myung, Jung-Jae,Park, Jin-koo,Chung, Yong-Sun,Kyong, Jin-Bum,Kim, Ho-Kun 한국공업화학회 1997 공업화학 Vol.8 No.5

n-propanol 용매내에서 titanium n-propoxide($Ti(O^nPr)_4$)의 가수분해반응에 의하여 $TiO_2$ 미분말을 합성하였고, 가수분해속도를 자외선 분광법에 의하여 측정하였다. 분말합성은 water/alkoxide의 농도비가 약 300정도에서 실시하였으며, 물농도, 반응온도, 반응시간 및 반응용액의 산 염기효과에 의한 합성조건을 조사하였다. 반응은 $Ti(O^nPr)_4$의 농도에 비하여 물농도를 과량으로 하여 유사일차반응으로 진행시켰고, 반응속도상수를 Guggenheim method로 계산하였다. 또한 물의 동위원소효과($D_2O$)를 측정하여 반응에 관여하는 물분자의 촉매성을 확인하였다. 실험결과 중성 및 염기성 용액 조건에서 $TiO_2$미분말이 합성되었고, 미세구조 관찰로부터 $TiO_2$입자는 직경 $0.4-0.7{\mu}m$ 정도의 구형입자로 확인되었으며, 물의 농도와 반응온도가 증가할수록, 반응시간이 감소할수록 입자크기는 작아지는 경향을 보였다. 물의 동위원소효과로부터, 물분자는 nucleophilic catalysis로 작용하고 있으며, 반응속도로부터 전이상태에 참여하는 n-value와 열역학적 파라미터를 계산한 결과, $Ti(O^nPr)_4$의 가수분해반응은 이분자 반응인 associative $S_N2$ mechanism으로 진행하는 것으로 추정되었다. $TiO_2$ powders were synthesized via hydrolysis reaction of titanium n-propoxide in n-propanol solvent and the reaction rates were studied by use of UV-vis spectroscopic method. Concentration of water, reaction temperature, reaction time and acid-base effects of the solution were investigated to determine the optimum conditions for $TiO_2$ powder synthesis. The reaction were controlled to proceed to pseudo-first orders reaction in the presence of excess water in n-propanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reaction using $D_2O$ was also carried out to determine the catalytic character of water. $TiO_2$ powders were synthesized only in the neutral and basic solution and those were almost spheric forms having average particle size of $0.4-0.7{\mu}m$ diameter. Particle size decreased with increasing concentration of water and reaction temperature, however, increased with increasing reaction time. Associative $S_N2$ mechanism for the hydrolysis was proposed from the data of n-value in the transition state and thermodynamic parameter. $D_2O$ solvent isotope effect showed that $H_2O$ molecules reacted as nucleophilic catalysis.

Titanium isopropoxide의 가수분해에 의한 TiO₂ Power 합성

박찬웅,명중재,김호건 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-

Isopropanol 내에서 titanium isopropoxide의 가수분해반응속도를 자외선분광법에 의하여 측정하였다. H₂O 농도 및 온도의 변화에 따른 반응속도상수를 Guggenheim method로 계산하였다. 이 실험 결과 titanium isopropoxide의 가수분해반응은 이분자 반응이 ?? mechanism 으로 관여하는 것으로 추정되었다. 또한 titanium isopropoxide의 가수분해에 의한 TiO₂ 분말합성에 있어서 pH 및 온도영향을 연구하였다. 합성된 분말과 소결체에 대하여 SEM, XRD, IR 및 입도분석을 통하여 characterization 하였다. TiO₂분말 합성결과 pH가 높을수록, 또한 반응온도가 높을수록 반응시간이 짧아졌으나, 낮은 온도에서 반응시킬 경우에 입자의 agglomeration이 적어짐을 알았다. 생성된 입자는 비정질의 gel 상태였으며, 소결시킨 후는 rutile, 또는 rutile과 anatase의 혼합물인 titanium dioxide인 것으로 나타났다. 소결하기 전의 TiO₂ 분말의 IR분석에서는 -OH, -CH₃ 등 유기물 그룹의 흡수 피크가 나타났으나 소결한 후의 시료에서는 그러한 피크가 나타나지 않았다. Rates of hydrolysis of titanium isopropoxide in isopropanol were investigated by UV spectroscopy. The change of reaction rate according to temperature and concentration of H₂O was calculated by Guggenheim method. From these results, it could be estimated that the hydrolysis of titanium isopropoxide was ?? mechanism involving both of titanium isopropoxide and H₂O. pH and temperature dependence of TiO₂ powder preparation were also investigated. Particle sizes and size distributions of dried powders were determined using size distribution analysis and SEM(scaning electron microscope), and the crystal phases in dried powder and in sintered powder were analyzed using powder XRD method. The reaction rate of TiO₂ powder preparation was faster at higher temperature and higher pH, however more agglomeration of particles occured at high temperature. The phase of dried powders was noncrystalline gel state but the sintering of the powder at 800℃ changed its phase to crystalline rutile or anatase. Absorption peaks of organic group such as -OH, -CH₃ in IR spectra of dried powder disappeared after sintering.

Synthesis of $TiO_2$ Powders by the Hydrolysis of Titanium n-Butoxide and Reaction Mechanism

박진구,명중재,정용선,경진범,김호건,Park, J.K.,Myung, J.J.,Chung, Y.S.,Kyong, J.B.,Kim, H.K. Korean Chemical Society 1999 대한화학회지 Vol.43 No.5

n-butanol 용매 내에서 titanium n-butoxide의 가수분해 반응에 의하여 $TiO_2$ 분말을 합성하였고, 가수분해 반응 메카니즘은 UV-Vis 분광법에 의하여 조사하였다. 가수분해 반응시 물의 농도를 과량으로 하여 반응이 유사일차반응으로 진행하도록 하였다. 이러한 농도 조건에서 얻어진 분말의 상(phase)을 XRD에 의하여 확인하였으며 반응속도는 Guggenheim method를 이용하여 계산하였다. 합성 결과 얻어진 분말은 생성 초기 비결정 상태에서 열처리 과정을 거치면서 rutile 구조로 상전이 하였다. 속도상수로부터 얻어진 물분자수(n-value)와 열역학적 파라미터로부터 titanium n-butoxide의 가수분해 반응은 Interchange-Associative(Ia)메카니즘으로 진행하는 것으로 추정되었다. $TiO_2$ powders were prepared via hydrolysis of titanium n-butoxide in n-butanol and hydrolysis mechanism of titanium n-butoxide was studied using UV-Vis spectrometer. Hydrolysis reactions were controlled to proceed to pseudo-first order reaction in the presence of excess water. The phases of $TiO_2$ powders, prepared under the these conditions, were identified by XRD and reaction rates were calculated by Gugggenheim method. Prepared powders were noncrystalline states in their initial stage of formation but transformed to crystalline rutile structure by heating. Reaction mechanism of titanium n-butoxide was proposed as Interchange-Associative(Ia) mechanism, based on the data of n-value and termodynamic parameters which were determined from the rate constants.

Flux법에 의한 초전도체 YBa2Cu3O7-x 단결정 육성

오근호,김호건,명중재 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.1

YBa2Cu3O7-x(=YBCO) single crystals were grown by flux method and the growing process of crystals was investigated. YBCO and 3BaO-7CuO composition powders were mixed by the ratio of 25 : 75(wt%), and the mixtures were melted at 105$0^{\circ}C$ in a electric furnace with no temperature-gradient. Then the melt was cooled at a rate 2-1$0^{\circ}C$/h in the above furnace. YBCO single crystal plate with average size of $1.5\times$2.0$\times$0.1㎣ were obtained in the cavities between crucible and solidified ingot, and the single crystals were oriented to <001> direction. The ingots of flux parts were analyzed by XRD and EDS for the purpose of presuming the growing process of the crystals. It was assumed that the divorced eutectic reaction, by which YBCO crystals were grown first and then BaCuO2 and CuO crystals, occured in the case of cooling rate faster than 2$^{\circ}C$/h. When the cooling rate was 2$^{\circ}C$/h, it was assumed that quasi-equilibrium eutectic reaction occured, so that YBCO, BaCuO2 and CuO crystals were grown at the same time.