Sr이 치환된 $ErCrO_3$고용체의 전기전도도

형경우,권태윤 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.12

페롭스카이트 구조를 갖는 E $r_{1-x}$S $r_{x}$Cr $O_{3-y}$ 계에서 x=0.0, 0.05, 0.1, 0.2인 비화학양론적 화합물 고용체를 1573 K 대기압 하에서 제조하였다. X-선 회절분석을 통하여 제조된 모든 계들이 등방정계 단일상을 형성하였고, 또한 반지름이 큰 S $r^{2+}$를 doping 시켜줌에 따라 격자상수 및 환산부피가 증가됨을 알 수 있었으며, 단위 세포의 부피는 직선성을 보이며 증가하였다. TG-DTA에 따른 열분석 결과 Sr이 치환되지 않은 계에서는 상전이가 발생하는 반면, x값이 0.05 이상인 계들은 고온영역에 이르기까지 등방정계에서 마름모정계로의 상전이가 억제되었다. 전자현미경을 통하여 치환된 Sr의 몰비에 따른 시료들이 미세구조를 관찰하였고, d.c 전도도 측정을 통하여 다결정성 시료계들이 가지는 전도도의 온도 의존성으로부터 구한 활성화 에너지는 0.17 eV였다.다.

층전하밀도 변화에 따른 Hydrotalcite형 LDH의 물리화학적 특성에 관한 연구 : Ⅱ. TG-DTA를 이용한 열적특성

형경우,이용석 전주대학교 자연과학종합연구소 1996 전주대학교 자연과학연구소 학술논문집 Vol.9 No.2

Layered double hydroxides (LDH) are antitypes of 2:1 layered aluminosilicates, [Mg_1 _xAl_x(OH)_2·(A^n)_x/n·yH_2O]. These structures consist of a positively charged framework in which the cations occupy the octahedral sites between the sheets of close-packed anions. Its was successfully synthesized by the co-precipitation methods and with variation of charge density which has a very important role to be determined the physicochemical properties of layered materials. From the results of TG--DTA analysis, we found that the thermal decomposition shows three stages of weight loss. The first and second steps stand the weight loss for dehydration reaction of interlayer water. The third step (at <450℃) is probably due to both the loss of structural water (dehydroxylation) and the deintercalation of anions occupied in the gallery space. It was also revealed that the transition temperature(T_c) and the weight loss were increased by increasing of layer charge of LDH.

PVA intercalated Montmorillonite-Cement System의 기계적 성질에 관한 연구

형경우 전주대학교 1999 論文集 Vol.24 No.2

PVA, montmorillonite and PVA intercalated montmorillonite were admixed in the system of cement paste in order to improve the mechanical strength. The compressive strength could not be improved by PVA-cement system and was rather decreased with addition amount. Montmorillonite-cement systems have different values of compressive strength according to the loading orientation and its value (perpendicular to the montmorillonite layer) was 2 times more than that of cement system. The compressive strength of PVA intercalated montmorillonite-cement system showed maximum value of 750 kgf/cm^(2) at the addition amount of 0.1% and was saturated(∼550 kgf/cm^(2)) as the addition amount increased.

??????-montmorillonite의 특성화 및 Deintercalation 반응의 반응속도 연구

형경우 全州大學校 1985 論文集 Vol.14 No.-

The layer charge density of montmorillonite (obtained from Yongil area, Korea) was calculated precisely by alcanol method, ~0.34 per unit chemical formua. The activation energy and the reaction order of deamine reaction for the synthesized decylammonium derivative were discussed by means of T.G.A.

알킬다이암모늄을 이용한 층상규산알루미늄염의 층전하밀도 측정

형경우,강준건,이용석 Natural Science Research Institute JEONJU UNIVERSI 1995 전주대학교 자연과학연구소 학술논문집 Vol.8 No.2

A new method for the layer charge determination in the 2:1 type layered aluminosilicate was proposed. As a test material vermiculite was chosen and its n-alkyldiammonium intercatation compounds were prepared by the ion exchange reaction. The layer charge density per formula unit (ξ) was estimated from the critical carbon number of alkyldiammonium ion during the structure phase transition (from monolayer to bilayer structure). The prepared compounds were also characterized by IR, XRD and Thermal Analysis.

Montmorillonite의 탈수반응에 대한 열화학적 특성에관한 연구

형경우 全州大學校 1988 論文集 Vol.17 No.-

This paper was studied to discuss the thermochemical and kinetic behavior of the dehydration reaction for the montmorillonites. The layer charge densities of the used montmorillonites could be calculated from the basal spacings of n-decylammonium derivatives under n-alcanol, and their values are 0.25, 0.38 respectively. Through the thermal analysis experiments, the dehydration enthalpies were measured to be 45.11, 48.21 KJ/mole of H₂O. For the kinetic study of dehydration reaction along with the estimation of activation energy, Kissinger's and Ozawa's methods were employed by using a differential scanning calorimetry(DSC), and the activation energies were estimated to be 35.9, 339 (Kissinger's method) and 39.7, 38.0 kJ/mol(Ozawa's method), respectively.

전이금속으로 치환된 Spinel형 LiMn$_{2-y}$M$_y$O$_4$(M=Cr$^{3+}$)의 구조 및 전기적 성질

형경우,김중헌,권태윤 한국세라믹학회 1999 한국세라믹학회지 Vol.36 No.9

For LiMn2O4 based spinel structures the stoichiometric reaction conditions need be considered carefully because the electrical properties depend on the structural stability. In order to obtain the homogeneous compound the Pechini process was chosen which could obtain a stoichiometry phase even low temperature and dependency of the synthetic condition on structural stability and electrochemical performance was investigated. X-ray diffraction studies showed that the compounds doped with transition metal have smaller lattice constants than those un doped. The dc conductivity was evaluated by a four probe method in the low and high temperature region respectively. The variations of basal spacings for the cathode were detected to be dependent on the extent of current flows (under dc)

界面活性劑 添加에따른 프라스틱 콘크리트의 物性變化 : - N. B. R. Latex에 대한 P.O.E. Nony Phenol Ether의 영향 - - The Effect of P.O.E. Nonyl Phenol Ether on the N.B.R. Latex Modified Mortar -

형경우,이홍림,김창은 연세대학교 대학원 1980 延世論叢 Vol.17 No.1

NBR latex was used as the admixture in order to improve the mechanical strength and the resistance of water absorption of the cement mortar. The effects of surfactant as additive on the fundamental properties of NBR latex modified hydraulic cements were studied. The results obtained are summarized as follows; 1. The water/cement ratio is decreased with increasing amounts of surfactant, as additive. 2. The resistance of water absorption and the compressive strength of plastic concrete are increased with increasing amounts of surfactant. 3. Because the factor influencing the compressive strength would rather depend on the coagulation of NBR latex film dispersed homogeneously than the properties of the hydrates of cement, NBR latex modified mortar cured under 50% of relative humidity shelved higher strength than the mortal cured at wet condition.

Pillar Host Material로써 Layered(Mg/Al) Double Hydroxide의 물리화학적 특성화

형경우,이용석 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.5

Layered double hydroxides(LDHs) [{{{{ {Mg }_{1-x } }}{{{{ {Al }_{x } }}({{{{ {OH}_{2 } }})]ζ+({{{{ {CO }`_{3 } ^{2- } ){ }_{x/2 } }}$.${{{{ { yH}_{2 }O }} wioth variation of layer charge densitywere synthesized by co-precipitation methdo since their charge densities have a very important role to be det-ermined the physicochemical properties of layered materials. The XRD IR and thermal studies of them were discussed and the kinetic study for the decarbonation reaction was also carried out. From the results of XRD analysis we found that the lattice parameter and the unit cell volume were linearly decreased with the amount of Al substituents(x) in the vicinity of x=2∼10${\times}$1/3${\times}$10-1 but they had nearly constant values when the x are far from these vicinit. The activation energies for the decarbonation reaction of x=6.8, 10${\times}$1/3${\times}${{{{ { 10}^{-1 } }} were estimated to be 47.0, 37.6, 39.3 kcal/mol The specific surface areas(90-120 m2/g) of stable hy-drotalcite-type LDHs were dractically decreased with increasing of layer charge density.

순환전압전류법과 일정전류전위차법을 이용한 PBD와 PVK의 이온화에너지, 전자친화도 및 전기화학적 특성에 관한 연구

형경우,최돈수 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.12

The effects of molecular structure on the redox properties are explored by the cyclic voltammetry, constant current potentiometry and spectroscopy using the thin films of organic electroluminescence materials of Poly(N-vinylcarbazole); PVK and 2- (4'-tert-butylphenyl) -5-(4"-bisphenyl) -1,3,4-oxadiazole; PBD. The UV/visible absorption maxima and band gap (E$\_$g/) show at 310nm (4.00eV) and 368nm (3.37eV) for FBD, 344nm (3.60eV) and 356nm (3.48eV) for PVK, respectively. The measured electrochemical ionization potential (IP) and electron affinity (EA) of these materials we 5.87 and 2.82eV for PBD, 5.80 and 3.17eV for PVK, respectively. The electrical band gaps are 3.05eV for PBD and 2.78eV for PVK, respectively. The electrical hole gap and electron gap with respect to the first rising potentials and the inflection potentials are obtained to be 0.39V and 0.41V for PBD, 0.25V and 0.28V for FVK, respectively.