• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.51-67
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• 1999

The growth of crystals with high melting points tfus$\geq$1$600^{\circ}C$ faces the researcher with experimental problems, as the choice of materials that withstand such high t is rather limited. Many metallic construction materials are in this high t range already molten or exhibit at least a drastically reduced mechanical strength. The very few materials with tfus》1$600^{\circ}C$ as e.g. W, Mo, and partially even Ir are more or less sensitive against oxygen upon heating. Whenever possible, high t crystal growth is performed under inert atmosphere (noble gases). Unfortunately, any oxides are not thermodynamically stable under such conditions, as reduction takes place within such atmosphere. A thoroughly search for suitable growth conditions has to be performed, that are on the one side "oxidative enough" to keep the oxides stable and on the other side "reductive enough" to avoid destruction of constructive parts of the crystal growth assembly. The relevant parameters are t and the oxygen partial pressure pO2. The paper discusses quantitatively relevant properties of interesting oxides and construction materials and ways to forecast their behavior under growth conditions.r growth conditions.

• Bulletin of the Korean Chemical Society
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• 제21권10호
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• pp.1041-1043
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• 2000

We present the effects of temperature (between 10 K and 298 K) and of hole concentration on the frequency and intensity of characteristic phonons in polycrystalline $La_2CuO_4-related$ compounds using FT-IR spectros-copy. The influences of the concentration of carrier doped on the phonon modes are prominent in the IR spectra of $La_2CuO_4-related$ compounds. For $La_2-xSrxCuO_4({\chi}=$ 0.00, 0.03, 0.07, 0.10, and 0.15) and electrochemically (or chemically) oxidized $La_2CuO_4$, the intensities of the transverse oxygen mode around 680cm $-^1$ which cor-responds mainly to Cu-O(1) stretching vibration in the basal plane of CuO6 octahedron, are decreased and dis-appeared depending on the Sr-substitution rate and the amount of excess oxygen, while the longitudinal oxygen mode around 510 cm $-^1$ corresponding to the Cu-O(2) stretching in the basal plane of CuO6 octahedron are near-ly invariable. In particular, after two cycles of cooling-heating between 10 K and 298 K for these sample, the phonons around 680 cm $-^1$ are blue shif 13-15 cm $-^1$, while the phonons around 510 cm $-^1$ are nearly constant. The introduction of the charge carrier by doping would give rise to the small contraction of CuO6 oc-tahedron as Cu $^3+$ requires a smaller site than Cu $^2+$, which results in the shortening of the Cu-O(1) bond length and Cu-O(2) bond length with the increased La-O(2) bond length. These results in the frequency shift of the characteristic phonons. The IR spectra of $La_2Li0.5Cu0.5O_4$ which exhibits an insulator behavior despite the $Cu^3+$ of nearly 100%, corroborate our IR interpretations. The mode around 710 cm $-^1$ corresponding to Cu-O(1) stretching vibration is still strongly remained even at low temperature (10 K). Thus, we conclude that the con-duction electrons formed within $CuO_2$ planes of $La_2CuO_4-related$ superconductors screen more effectively the transverse oxygen breathing mode around 680 $cm-^1$ depending on the concentration of the doped charge carrier in $La_2CuO_4-related$ compounds, which might use as a superconductivity probe.

• 한국결정성장학회지
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• 제26권1호
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• pp.28-34
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• 2016

원적외선 방사세라믹은 인체의 피부 안쪽으로 깊숙이 적외선을 침투시켜 온열 및 치료환경을 주는 매력적인 재료로써, 열적 치료 장치, 온열 매트, 히터 등과 같은 분야에 많은 응용이 되고 있다. 본 연구에서는 소결 온도와 시간을 변화시킴으로써 높은 방사율을 가지는 원적외선 방사세라믹의 소결 조건을 최적화하고자 하였다. 원적외선 방사체의 상 분석은 XRD로, 그 파단면의 미세구조는 SEM을 이용하여 분석하였다. 원적외선 방사율의 측정은 FT-IR으로 행하여, 결과를 종합적으로 해석하여 소결체의 최적 공정 조건을 확립하였다.

• Elastomers and Composites
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• 제35권4호
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• pp.272-280
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• 2000

범용고무인 NR, IR, BR, SBR 1500, SBR 1700의 열분해 특성에 대한 속도론적 해석을 실험데이터를 이용하여 수행하였다. 열분석법을 사용하여 범용고무의 속도론적 해석을 수행하였으며, Kissinger 방법, Friedman 방법, Ozawa 방법에 의한 NR의 활성화 에너지는 각각 195.0, 198.3, 186.3 kJ/mol로 나타났으며, SBR 1500의 활성화에너지는 각각 246.4, 247.5, 254.8kJ/mol이었다. 열분해 공정의 생성물은 전반적으로 최종 온도가 증가함에 따라 증가하는 경향을 나타내었다. 가열 속도의 영향에 따른 오일의 수율 증감은 각 시료마다 차이를 보이고 있었다. SBR 1500의 열분해 후 회수된 오일의 수평균 분자량은 740-2486로 나타났다. 또한 발열량을 측정한 결과 39-40kJ/g의 발열량을 나타내었는데, 이러한 값은 현재 연료로 사용되고 있는 kerosene, diesel, 경유, 중유의 발열량보다는 작은 것이지만 연료로서의 에너지 준위가 양호한 것으로 판단된다.

• 대한기계학회논문집B
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• 제36권7호
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• pp.675-681
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• 2012

본 연구는 낮은 회 성분의 함량과 높은 발열량의 특성을 지닌 초청정 석탄의 촤 반응율 특성을 알아보았다. 실험은 DTF(Drop Tube Furnace)를 통해서 다양한 온도조건 하에 산소의 분율을 바꾸어가며 수행하였다. 촤 반응률을 도출하기 위하여 FT-IR을 통해 배기가스(CO, $CO_2$)를 측정하였으며, 이색온도계를 통하여서 입자 온도를 측정하였다. 또한, Arrhenius 경험식을 토대로 초청정 석탄 촤의 활성화 에너지와 빈도인자를 도출하였다. 결과는 초청정 석탄 촤의 반응특성은 온도와 산소 분율이 높아질수록 뚜렷한 증가를 보였고, 초청정 석탄 촤의 활성화 에너지는 역청탄의 수치와 비슷한 값을 보임을 알 수 있었다.

• 공업화학
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• 제26권6호
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• pp.681-685
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• 2015

본 연구에서는 열 변색 물질로 알려진 순수한 $BiVO_4$ 분말과 금속이 도핑된 $M-BiVO_4$ (M = Mg, Cu) 분말들을 bismuth nitrate ($Bi(NO_3)_3$)와 ammonium vanadate ($NH_4VO_3$)의 혼합 수용액으로부터 고압반응기에서 수열 합성법을 통하여 성공적으로 제조하였다. 시료들의 결정구조, 미세구조 및 열 변색 특성들은 FE-SEM, FT-IR, XRD, DSC, UV-Vis-NIR 분광기 및 colorimeter를 이용하여 분석하였다. 시료를 상전이 온도 이상으로 가열시키면, 순수한 $BiVO_4$ 시료에 비하여 $M-BiVO_4$ (M = Mg, Cu) 시료의 색상이 상대적으로 선명하게 열 변색하였다.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2257-2262
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• 2014

$C_{60}$ is widely investigated because of its unique structure. But its applications in solid propellant seem to be relatively neglected. $C_{60}$ has more outstanding features than carbon black which is widely used as a catalyst ingredient of solid propellant. To combine the advantages of fullerene and lead salts, another good composite in propellant catalysts, we synthesized a kind of fullerene phenylalanine lead salt (FPL) and explored its thermal performances by differential thermal analysis (DTA) and thermogravimetry analysis (TGA). The results show it undergoes four exothermic processes started from 408 K. Combined TGA and X-ray diffractometer (XRD), the decomposition mechanism of FPL was derived by TG-IR and comparing IR spectra of FPL and its residues after burned to $327^{\circ}C$, $376^{\circ}C$ and $424^{\circ}C$, respectively. Effect of FPL on the decomposition characteristic of hexogen (RDX), a type of explosive in propellant, has been investigated using DTA at different heating rate, which shows the decomposition temperatures of the explosive are all reduced by more than 20 K. The corresponding activation energy ($E_a$) is decreased by $30kJ{\cdot}mol^{-1}$. So FPL has potential application as a combustion catalyst in solid propellant.

• 한국자동차공학회논문집
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• 제23권2호
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• pp.199-207
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• 2015

Solid materials of ammonia sources with SCR have been considered for the application of lean NOx reduction in automobile industry, to overcome complex problems of liquid urea based SCR. These solid materials produce ammonia gas directly with proper heating and can be packaged by compact size, because of high volumetric ammonia density. Among ammonium salts and metal ammine chlorides, calcium ammine chloride was focused on this paper due to low decomposition temperature. In order to make calcium ammine chloride in lab-scale, simple reactor and glove box was designed and built with ammonium gas tank, regulator, and sensors. Basic test conditions of charging ammonia gas to anhydrous calcium chloride are chosen from equilibrium vapor pressure by Van't Hoff plot based on thermodynamic properties of materials. Synthetic method of calcium ammine chloride were studied for different durations, temperatures, and pressures with proper ammonia gas charged, as a respect of ammonia gas adsorption rate(%) from simple weight calculations which were confirmed by IC. Also, lab-made calcium ammine chloride were analyzed by TGA and DSC to clarify decomposition step in the equations of chemical reaction. To understand material characteristics for lab-made calcium ammine chloride, DA, XRD and FT-IR analysis were performed with published data of literature. From analytical results, water content in lab-made calcium ammine chloride can be discovered and new test procedures of water removal were proposed.

• 한국재료학회지
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• 제18권5호
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• pp.235-240
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• 2008

This paper presents results and observations obtained from a study of the optical and thermal properties of alkali tellurite depending on the composition. Fourier transform infrared (FT-IR) spectra showed evidence of chemical modification from $TeO_4$ trigonal bipyramids (tbp) to $TeO_3$ trigonal pyramids (tp) in tellurite glasses. The optical band gaps of the different glass samples calculated using Tauc's method were found to range from 3.5-3.8 eV. The glass transition temperature (Tg) and glass stability (${\Delta}T$) of alkali tellurite glasses were investigated, as $M_2O$ [M: Li, Na, K] amounted to 25 mol%, through the use of differential thermal analysis (DTA). The coefficient of thermal expansion (CTE) was measured in a thermo mechanical analysis (TMA) with a slow heating rate after the glass samples were annealed. The results confirm that the optical band gap of alkali tellurite glasses depends on the Te-O-Te structural relaxation related to the ratio of bridging/non bridging oxygen (BO/NBO). In contrast, the thermal properties are related to the ionic field strength of the Te-O-M and M-O-M bonds, and the Te-O-Te breakage depends on the ratio of BO/NBO.

• 한국식품과학회지
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• 제25권3호
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• pp.214-219
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• 1993

pH7.0으로 조절한 2M의 AsA 용액을 $85^{\circ}C$에서 25시간 갈변반응시켜서 생성된 물질 중 항산화효과를 지닌 물질을 분리하고 성질을 조사하였다. 투석내액 및 투석외액 갈변반응물질 모두 항산화성이 존재하였고 투석외액 갈변반응물질의 항산화효과가 더 크게 나타났다. 투석외액 갈변반응물질을 gel 여과하여 분리된 3가지 획분(A, B, C)중 갈변도가 가장 높고 환원력이 가장 낮은 획분(C)의 항산화효과가 가장 크게 나타났다. 항산화성이 중간정도인 획분(B)은 환원력의 세기와 갈변도가 세획분중 중간정도에 속하였고 환원력은 가장 높고 갈변도가 가장 낮은 획분(A)은 항산화효과가 가장 낮았다. UV-Visible spectrum에서 A획분과 B획분은 각각 266.1 및 257.4nm에서 최대흡광 peak를 나타냈으나 C획분은 274.8nm에서 약한 peak를 나타내었다. IR-spectrum 조사결과 A, B 및 C획분 모두 hydroxy 및 carboxylic group이 존재하였고 항산화성이 큰 B와 C분획은 carboxylic ester이었다.