산화툴륨의 결함구조와 전기전도성에 대한 연구

최재시,정원양,김진호,이창환 연세대학교 자연과학연구소 1985 學術論文集 Vol.14 No.-

산화툴륨의 전기전도도를 400~1100℃의 온도영역과 10^-6~10^-1atm의 산소분압범위에서 측정하였다. 일정한 산소분압에서 전기전도도의 대수값을 절대온도의 역수에 대하여 도시한결과 직선관계를 얻었으며 inflection point가 나타났다. 활성화에너지는 고온영역에서 34.5kcal/mole, 저온영역에서 19.3kcal/mole이었다. 전기전도도의 산소분압의존성은 직선관계를 나타내었으며 600~1100℃의 온도영역에서 σ∝Po_2^1/5.3, 400~600℃의 온도영역에서σ∝Po_2^1/6.3이었다. 고온영역에서의 주결함은 V_??이며, 저온영역에서는 O_?? 임이 밝혀졌다. 전도도의 온도 및 산소분압의존성을 해석하였으며, 전도메카니즘을 제시하였다. The electrical conductivity of thulium sesquioxide has been measured from 400 to 1100℃ under oxygen partial pressure (Po_2) of 10^-6 to 10^-1 atm. Plots of log conductivity vs. 1/T at constant Po_2 are found to be linear with inflection point and the activation energies obtained from the slopes are 34.5kcal/mole in the higher temperature region and 19.3kcal/mole in the lower temperature region. The Po_2 dependences of the electrical conductivity are found to be linear and closely approximated by σ∝Po_2^1/5.3 in the temperature range of 600-1100℃ and σ∝Po_2^1/6.3 in the range of 400-600℃. The dominant defect is V_?? in the higher temperature region and O_?? in the lower temperature region. The interpretations of conductivity dependences on temperature and Po_2 are presented and conduction mechanisms are suggested to illustrate the data.

CoO의 과잉산소량과 전기전도성에 관한 연구

최재시,여철현 연세대학교 대학원 1974 延世論叢 Vol.11 No.1

The excess oxygen of the polycrystalline cobaltous oxide has been measured by the gravimetric analysis in a temperature range from 500 to 1200℃ under oxygen pressures from 2×10-1 to 1.3×10-6 atm. And then the electrical conductivity of the oxide has been studied in the temperature range 600 to 1200℃ under oxygen partial pressures of 10-1 to 10-7 atm. The enthalpies of formation of excess oxygen were usually larger than -16 kcal/mole under the above conditions and the activation energies for the electrical conductivities of the oxide show that the energies in the temperature range 600 to 900℃ are greater than that in the temperature range 900 to 1200℃ at various oxygen pressures. The 1/n values obtained from the oxygen pressure dependence of the excess oxygen (or log Y= 1/n log Po2) and of the electrical conductivity (or log σ= 1/n log Po2) respectively, are shown similar tendency in changes of the values at various temperatures. The relations between the excess oxygen and the electrical conductivity of the oxide are discussed in this paper thoroughly.

ZnO 上에서의 일산화탄소의 산화반응에 관한 연구

崔在時,金保源 연세대학교 대학원 1972 延世論叢 Vol.9 No.1

The kinetic study on the oxidation reaction of carbon monoxide has been undertaken using n-type ZnO semiconductor as a catalyst between 260℃ and 350℃ at various oxygen and carbon monoxide pressures by applying the static method. The order of reaction between 260℃ and 320℃ was found to be 1.5, with ***** Pco Po1/22, and at 350℃ the Roginsky-Zeldovitsch equation, *****, fits well. The mechanism of this reaction was explained well by the n·type character of ZnO.

NiO-ZnO-Fe_2O_3 System의 물성에 관한 연구

최재시,김규홍,전종호,박광하 연세대학교 자연과학연구소 1984 學術論文集 Vol.13 No.-

NiO-Z_nO-Fe_2O_3계에 대하여, Solid Solution 을 이루는 적합한 조성관계와 여러가지 비율로 혼합한 페라이트에 대하여 자성, 전도성을 측정하였다. 각 시료의 비저항은 3×10^-6Ωcm이었고, α-Fe_2O_3, NiO, ZnO의 조성비가 50, 15, 35mol %인 페라이트가 가장 높은 μ와 Q값을 갖는다. physical-chemical properties and the best composition of the solid solution of the NiO-ZnO-Fe_2O_3 system were checked by Q-meter and electrometer. The resistivity of each sample is 3×10^-6Ωcm, and the best composition of nickel ferrite for radio frequency use is α-Fe_2O_3:NiO:ZnO=50:15:35(mol%).

NiO 촉매에 의한 CO 산화반응에 관한 연구

최재시,김규홍,Jae Shi Choi,Keu Hong Kim 대한화학회 1969 대한화학회지 Vol.13 No.4

The catalytic reaction between carbon monoxide and oxygen was investigated with the various nickel oxide catalysts at different partial pressures of carbon monoxide and oxygen and at reaction temperatures in the region of 120$^{circ}$to 250$^{circ}C$. The reaction has the highest rate with the nickel oxide catalyst which is sintered at low temperature. A reaction mechanism to explain the data is derived. From the Arrhenius equation, the activation energies in the region of experimental temperatures are found to be from 5.49 to 9.15 kcal/mole. The concentration of excess oxygen in the nickel oxide seems to vary according to the sintering temperatures and periods and is the controlling factor in determining the type of kinetics followed by the catalytic reaction.

수소로 환원시킨 니켈도프된 α형 산화철상에서의 일산화탄소 산화반응메카니즘

최재시,오응주,전종호,원휘준,김돈,최찬유 연세대학교 자연과학연구소 1983 學術論文集 Vol.11 No.-

수소로 환원시킨 니켈도프된 α-Fe_2O_3의 촉매성이 CO산화반응을 통하여 150~250℃에서 연구되었다. CO의 산화속도는 CO에 대하여 1차이며 O_2에 대하여 0.5차 반응이었다. O_2는 수소환원에 의하여 생성된 산소공위에 흡착되고 CO는 흡착된 산소와 반응함을 확인하였다. 전기전도도 데이타는 산소의 흡착이 전기전도전자를 제거한다는 사실을 보여주었고, CO와 흡착된 O_2와의 반응이 전체 반응의 율속단계임을 규명하였다. The catalytic activity of "Hydrogen-Reduced" Ni-doped α-Fe_2O_3 has been investigated the oxidation of carbon monoxide at 150 to 250℃. The oxidation rates have been related with 1.5 order kinetics; first order with respect to CO and 1/2 with respect to O_2. Oxygen is adsorbed on oxygen vacancy that formed through H_2 reducing, on the other hand CO seems to react with already adsorbed oxygen. The conductivities show that adsorption of O_2 on oxygen vacancy withdraws the conduction electron from the vacancy and the reaction of CO with adsorbed oxygen is rate determining step for overall reaction.

Sm_2O_3 및 ZrO_2-Sm_2O_3 System의 전기전도도

최재시,김규홍,김용배,최찬유,원휘준 연세대학교 자연과학연구소 1983 學術論文集 Vol.11 No.-

분광학적 순도의 다결정성 Sm_2O_3의 전기전도도를 300~1000℃의 온도범위와 10_-5∼10_-2기압의 산소압력하에서 측정하였다. 전기전도도의 산소압력의 의존성과 온도의존성으로부터 본 시료의 결함구조와 전기전도 메커니즘을 연구하였다. 본 실험결과는 같은 산소압력 조건하(10_-5∼10_-1 기압)에서 낮은 온도 영역과 높은 온도영역으로 구분되었으며 높은 온도 영역(700~1000℃)에서 시료들의활성화 에너지는 27~29Kcal/mol이었다. 산소압력 의존도(1/n)는 (1/5.5)로 부터 (1/5.2)로 높은 온도영역에서 증가하는 p형 반도성을가졌으며, 일부 이온성을 가지는 전자성 전도성을 갖는 것으로 나타났다. 낮은 온도 영역에서의 전기전도 메카니즘은 small polaron model 에 의한 산화이온이 hopping 하므로써 전도성을 갖는 것으로 설명하였다. ZrO_2-Sm_2O_3의 전기 전도도는 원자가 조절원리에 따라 Zr^4+가 Sm^3+ site에 첨가되므로써 electron donor로 작용하고 전기전도도 값이 현저하게 증가된다. 전기전도도 메커니즘은 polaron model 에 따르나 impurity control semiconductor로서 중요하다. The electrical conductivities of highly pure polycrystalline Sm_2O_3 have been measured over the temperature range of 300 to 1000℃ under the oxygen pressure range of 10_-5 to 10_-1 atm. The defect structure and the type of this semiconductor and the electrical conduction mechanism are investigated by measuring the temperature and oxygen pressure dependence of the electrical conductivity. The activation energies of Sm_2O_3 are 27-29 Kcal/mol at higher temperature region, and 8-10 Kcal/mol at lower temperature region. The oxygen pressure dependences of electrical conductivity, σ∝FO_2^1/n, are characterized by n values of about 5.2 at 1000℃, 5.5 at 600℃. The sesquioxide exhibits mixed conduction with some ionic conduction and major electronic conduction carriers. According to the principle of controlled valency, the electrical conductivity of ZrO_2-Sm_2O_3 system increase due to the electron donation of doped Zr^4+ in Sm^3+ site of Sm_2O_3. Electrical conduction mechanism is followed by polaron model and impurity doping is important as a impurity control semiconductor.

고체표면의 흡착현상에 의한 촉매개발연구

崔在時,韓賢洙,金奎弘,崔承洛 연세대학교 자연과학연구소 1978 學術論文集 Vol.2 No.-

CO 및 SO_2의 산화반응을 α-Fe_2O_3를 사용하여 각종 산소압력하에서 200~350℃(CO) 및 220~280℃(SO_2) 흡착기구와 아울러 속도론적 연구를 실시하였다. CO산화반응에서 E_a=10.8kcal/mole및 -dp/dt=k P_co P_o2^0.5이며 SO_2 산화반응에 대하여는 -dp/dt=kP_so_2 P_o_2^0.5 및 E_a=18.8 kcal/mole 임을 확인하였다. CO 산화반응에 대한 mechanism은 흡착 site인 산소공위 V_o-2e´및 철의 interstitial site인 Fe^2+로서 설명하였으며 SO_2반응에 대하여도 vacancy mechanism을 들어 설명하였다. 특히 rate determining step은 전기전도도 측정법으로 극히 성공적인 뒷받침아래 결정하였다. The catalytic oxidation of CO has been investigated in the presence of vacuum activated α-Fe_2O_3 under various partial pressures of CO and O_2 at temperatures from 200 to 350℃. The oxidation rates have been correlated with 1.5 order kinetics; first-order with respect to CO and 0.5 order for O_2. CO appears to be adsorbed essentially in an ionic, while O_2 is adsorbed in an ionic as well as a non-ionic species. Two surface sites, probably Fe_i^2+ interstitial and oxygen vacancy, might be required to adsorb CO and O_2. The conductivity data show that the adsorption of CO exceeds the O_2 adsorption and indicate that the adsorption process of CO (CO(g)→CO^+(ads)+e^-) in the rate determining step. From the agreement between the kinetic data and conductivity measurements, the oxidation mechanism of CO and the defect structure of the vacuum-activated α-Fe_2O_3 are suggested.

NiO의 Semiconductivity에 關한 硏究

최재시,여철현,Choi, Jae-Shi,Yo, Chul-Hyun 대한화학회 1968 대한화학회지 Vol.12 No.2

The conductivity of polycrystalline NiO is measured in the temperature range of $200^{\circ}C\;to\;800^{\circ}C$ under oxygen pressures from $1.52{\times}10^2\;mmHg\;to\;10^{-4}$ mmHg. The plots of the log ${\sigma}$ vs 1/T at constant oxygen pressure are found to be linear and the activation energies obtained from the slopes of these plots show that the energies are greater under high oxygen pressure than under low pressure. The transition points are found from the curves. The dependence of the conductivity on the $O_2$ pressure, in the above temperature range, is to be regular but it does not obey the theoretical expression, i.e. ${\sigma}=K_{ox}P^{1/6}.$ The activation energies are calculated from the curves at the various condition.

NiO-$Y_2O_3$계의 전기전도성

최재시,김규홍,정원양,Jae Shi Choi,Keu Hong Kim,Won Yang Chung 대한화학회 1986 대한화학회지 Vol.30 No.1

Electrical conductivities of NiO-$Y_2O_3$ systems containing 0.8, 1.6, and 3.2 mol% NiO have been measured in the temperature range of 400 to 1100$^{\circ}$C at $PO_2$'s of 1 ${\times}10^{-5}$ to 2 ${\times}10^{-1}$ atm. Plots of $log\sigma$ vs 1/T at constant $PO_2$'s are found to be linear with an inflection at temperature around 650$^{\circ}$C. The slopes are steeper in the high temperature region above 650$^{\circ}$C than in the low temperature region below 650$^{\circ}$C. The average activation energies are 41.8kcal/mol in the high temperature region and 12.5kcal/mol in the low temperature region. $PO_2$'s dependence value, 1/n, is 1/5.1~1/5.4 in the high temperature region and 1/5.9~1/6.2 in the low temperature region. The NiO-$Y_2O_3$ systems are found to be an electronic p-type semiconductor. The predominant defects in the systems are believed to be triply ionized yttrium vacancy in the high temperature region and doubly ionized oxygen interstitial in the low temperature region. Ionic contribution to the total conductivity is found from ${\sigma}^{\propto}PO_2$ in the temperatures below 650$^{\circ}$C. 0.8, 1.6 및 3.2 mol%의 산화니켈을 혼입한 산화니켈-산화이트륨계의 전기전도도를 1 ${\times} 10^{-5}$ ~ 2 ${\times}10^{-1}$ atm의 산소압력과 400 ~ 1100$^{\circ}$C의 온도영역에서 산소압력 및 온도의 함수로서 측정하였다. 전기전도도의 온도의존성은 약 650$^{\circ}$C부근에서 두 영역으로 나뉘었으며, 650$^{\circ}$C이하 영역보다 650$^{\circ}$C이상 영역에서의 온도의존성이 더 큰 것으로 밝혀졌다. 평균 활성화에너지는 650$^{\circ}$C이상 영역에서 41.8kcal/mol, 650$^{\circ}$C이하 영역에서 12.5kcal/mol이다. 산소압력의존성, 1/n값은 650$^{\circ}$C이상 영역에서는 1/5.1~1/5.4이며, 650$^{\circ}$C이하에서는 1/5.9~1/6.2이다. NiO-$Y_2O_3$계는 결함구조가 고온영역에서 3가로 이온화한 이트륨공위이며, 저온영역에서는 2가로 이온화한 틈새형 산소 인전자성 p-형 반도체임이 밝혀졌다. 그러나, 저온영역에서는 이온성 전기전도에 의한 기여가 어느 정도 존재하는 것으로 밝혀졌다.