• 공업화학
• /
• 제4권2호
• /
• pp.342-348
• /
• 1993

1473 K, 대기압하에서 $Sm_{1-x}Sr_xFe^{3+}{_{1-t}}Fe^{4+}{_t}O_{3-y}$ ($0.00{\leq}x{\leq}1.00$) 페라이트계에 대하여 균일상의 시료를 제조하였다. x값의 증가에 따라 $Fe^{4+}$ 이온의 양이 증가하였으며 결정학적 구조는 orthorhombic에서 cubic으로 변화함을 알 수 있었다. $Fe^{4+}$ 이온의 증가에따라 일정온도에서의 전기전도도는 급격히 증가하며, 활성화에너지는 감소한다. x=0.00 시료의$M{\ddot{o}}ssbauer$ spectrum은 six-line 형태를 보이며 팔면체 자리에 $Fe^{3+}$ 이온이 존재함을 확인시켜 주었다.

• 펄프종이기술
• /
• 제43권3호
• /
• pp.113-120
• /
• 2011

Precipitated calcium carbonate(PCC), particularly calcite crystal, is extensively used as a pigment, filler or extender in various industries such as paper, paint, textile, detergents, adhesives, rubber and plastics, food, cosmetics, and biomaterials. PCC is conventionally produced through the gas-liquid carbonation process, which consists on bubbling gaseous $CO_2$ through a concentrated calcium hydroxide slurry. This study is aimed to find some factors for controlling the morphology of engineered PCC in lab-scaled mixing batch. The experimental designs were based on temperature variables, $Ca(OH)_2$ concentration, $CO_2$ flow rate, and electrical conductivity. The model of engineered PCC morphology was finally controlled by adjustment of electrical conductivity(6.0~7.0 mS/cm) and $Ca(OH)_2$ concentration(10 g/L). Orthorhombic calcite crystals were mostly created at high concentration and electrical conductivity conditions because the increased ratio of $Ca^{2+}$ and $CO{_3}^{2-}$ ions affects the growth rate of orthorhombic faces. Excess calcium spices were contributed to the growth of faces in calcium carbonate crystal, and the non-stoichiometric reaction was occurred between $Ca^{2+}$ and $CO{_3}^{2-}$ ions during carbonation process.

• E2M - 전기 전자와 첨단 소재
• /
• 제9권4호
• /
• pp.379-384
• /
• 1996

The microwave dielectric properties of (I-x)CaTiO$_{3}$-xLaAIO$_{3}$ were investigated. The solid solution of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ had the perovskite structure in the range of all compositions. The crystal system of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ was transformed to orthorhombic(x.leq.0.4), psudo-cubic(x=0.5), and rhombohedral (x.geq.0.7) in turn, as the amount of LaAIO$_{3}$ increased. The dielectric constant and temperature coefficient of resonant frequency of solid solution were decreased with the content of LaAIO$_{3}$, whereas, the value of Q . f$_{o}$ was increased. The microwave dielectric material having Q . f$_{o}$ = 32, 500, .epsilon.$_{r}$ = 42, and .tau.$_{f}$ = 5 ppm/.deg. C was obtained from the 0.35CaTiO$_{3}$-0.65LaAIO$_{3}$ composition sintered at 1600.deg. C for 4hrs.hrs.hrs.

• E2M - 전기 전자와 첨단 소재
• /
• 제9권4호
• /
• pp.404-409
• /
• 1996

The structural and electric properties of $Y_{1-x}$YbF$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-y}$(x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) have been investigated by using XRD(X-ray diffraction), TMA(thennomechanical analysis), NMR(nuclear magnetic resonance) analysis and four probe method. $Y_{1-x}$YbF$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-y}$ samples were prepared by conventional solid-state reaction method using $Y_{2}$O$_{3}$, BaCO$_{3}$, CuO and YbF$_{3}$ power. TMA and high temperature XRD results shows that orthorhombic to tetragonal phase transition occurs in the unfluorinated 1-2-3 sample while the phase change is not observed in the fluorinated 1-2-3 samples. Superconducting transition temperature(T$_{c}$) increases with increasing YbF$_{3}$ content ; T$_{c}$, of the sample reaching maximum of 102K for x=0.3, and then decreases with further increasing YbF$_{3}$ content. The structural analysis and T$_{c}$ results shows that the fluorine doping stabilize the orthorhombic phase, together with the increase in T$_{c}$.}$ c/.TEX> c/.

• 한국전기전자재료학회논문지
• /
• 제22권5호
• /
• pp.377-381
• /
• 2009

Tetragonal-NiSi (010)/Si superstructures were calculated for studying the interface structure using density functional theory, The orthorhombic-NiSi was changed to the tetragonal-NiSi to be matched with the Si surface for epitaxy interface. The eight interface models were produced by the type of the Si surfaces, The tetragonal-NiSi (010)/Si (020)[00-1] superstructure was energetically the most favorable, and the interface thickness of this superstructure was the shortest among the tetragonal-NiSi (010)/Si superstructures. However, in the case of tetragonal-NiSi (010)/Si (010)[00-1] superstructure, it was energetically the most unfavorable, and the interface thickness was the longest. The energies and interface thicknesses of tetragonal-NiSi (010)/Si superstructures were influenced by the coordination number of Ni atoms and the bond length between atoms located at the interface.

• 대한전자공학회논문지
• /
• 제26권4호
• /
• pp.62-66
• /
• 1989

$Bi_2S_3$다결정과 $Bi_2S_3$ 무정형 박막은 증착방법에 의해서 성장되었다. 측정된 격자상수들은 기판온도 $210^{circ}C$에서 $a=1.708{\AA},\;b=3.943{\AA} 그리고 $c=3.943{\AA}$이었으며, orthorhombic 구조를 가진것으로 나타내었다. 다결정 박막 $Bi_2S_3$energy은 $289^{circ}C$ 에서 1.375eV로 측정되었다. 674nm의 중심에서는 변화된 광자흡수 구조로 생각되어졌다.

• 한국결정학회지
• /
• 제7권1호
• /
• pp.20-29
• /
• 1996

(Sr1-xCax)CuO2 단결정을 융제법으로 제조하고 단결정 X-선 회절법을 이용하여 그 결정구조를 밝혔다. 이 화합물의 결정축계는 사방정계(orthorhombic system)이며, 공간군은 Cmcm(63), 그리고 격자상수 a, b, c는 각각 3.4645Å, 16.1417Å, 3.8727Å이었다. (Sr1-xCax)CuO2 화합물에서 Sr대신 치환되는 Ca이온의 한계를 구조적인 관점에서 연구하였다. 이를 위해 X-선 회절(CAD4), energy dispersive X-ray fluorescence (EDAX) and electron probe micro-analysis (EPMA) 등을 사용하였다. Ca가 치환됨에 따른 Cu-O 결합길이의 변화로부터 Ca의 치환한계를 결정하였는데 그 한계치는 Xca≒0.73이었다.

• 한국재료학회지
• /
• 제24권7호
• /
• pp.357-362
• /
• 2014

Thermal barrier coatings(TBCs) are being applied in many industrial fields such as thermal power generation, aviation and seasonal fields. $ZrO_2-Y_2O_3$(8%) thermal spray coating powders are commercially used as thermal-barrier coating materials to protect against oxidation and corrosion of heat-resistant alloys at elevated temperatures. Currently, $ZrO_2-Y_2O_3$(8%) thermal-spray powder is made using the industrial co-precipitation process, which is very complex and requires a lot of time. In this study, orthorhombic $ZrO_2$ and $Y_2O_3$ powders were fabricated by mechanical mixing, which is more economical than the co-precipitation process. A tetragonal, yttria-stabilized zirconia(YSZ) coating-layer was produced by plasma spraying, using orthorhombic $ZrO_2-Y_2O_3$(8%) powder. Our experimental results indicate that $ZrO_2-Y_2O_3$(8%) mixed powder can be used economically in industry because it is no longer necessary to make this powder by liquid and gas-phase methods.

• 반도체디스플레이기술학회지
• /
• 제7권2호
• /
• pp.45-48
• /
• 2008

An epitaxial $\beta-FeSi_2$ structure on Si (001) substrate was calculated by using density functional theory (DFT). Unit cell of orthorhombic $\beta-FeSi_2$ and $\sqrt{2}\times\sqrt{2}\times2$ supercell were calculated to find the energetically favorable structures first. The $\chi$- and y-direction axes of $\beta-FeSi_2$ were changed into y- and z-direction axes to match its structure with that of Si, to minimize the lattice mismatch between $\beta-FeSi_2$ and Si. Distance between the Si (001) surface and the $\beta-FeSi_2$ surface was varied to find an optimum distance between them, resulting in 0.825 $\AA$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.541-544
• /
• 2001

Orthorhombic LiMnO$_2$ was synthesized by solid-state reaction using LiOH$.$H$_2$O and Mn$_2$O$_3$ as starting material. Its electrochemical properties as cathode in lithium batteries were examined. X-ray diffraction revealed that the LiMnO$_2$ compound showed a well-defined orthorhombic phase of a space group with Pmnm. The capacity of LiMnO$_2$ agreed well with its specific surface area and grinding treatment was effective in improving cycling performance. For lithium polymer battery applications, the LiMnO$_2$ cell was characterized electrochemically by charge-discharge experiments. And the relationship between the characteristics of powder and electrochemical properties was studied in this research. A maximum discharge capacity of 160-170mAhg$^{-1}$ for LiMnO$_2$/Li cell was achieved