• 대한화학회지
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• 제17권2호
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• pp.122-125
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• 1973

시차열곡선에서 Pyrolusite $({\beta}-MnO_2)$의 결정 전이의 흡열 Peak를 이용하여 분석 화학적인 재현성을 검토한 결과 Pyrolusite의 량이 50mg∼450mg까지는 정량적이었다. ${\alpha}-MnO_2$는 흡열 Peak가 중첩되어 파의 분리가 불가능하였으며, ${\gamma}-MnO_2$(전해이산화망간)와 ${\delta}-MnO_2$는 오차 범위 ${\pm}5{\%}{\sim}{\pm}10{\%}$이내에서 조제시료중 Pyrolusite만을 정량할 수 있다.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1375-1378
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• 2014

In this study, maghemite (${\gamma}-Fe_2O_3$) nanoparticles were produced using gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared ${\gamma}-Fe_2O_3$ nanoparticles were characterized using XRD, FT-IR, TEM, SEM and VSM data. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced gelatin-$Fe_3O_4$ nanocomposite were examined to prove the fundamental effect of gelatin; both as a capping agent in the nanoscale synthesis and as the director of the spinel ${\gamma}-Fe_2O_3$ synthesis among possible $Fe_2O_3$ crystalline structures.

• Macromolecular Research
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• 제13권2호
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• pp.156-161
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• 2005

The thermal transitions of a nylon 6/layered silicate nanocomposite were studied by differential scanning calorimetry and in-situ synchrotron X-ray diffraction. The drawn film of the nylon 6/layered silicate nanocomposite typically showed three endotherms in the DSC thermogram; a very broad endotherm at $\sim120^{\circ}C(T_{1})$, a double-melting endotherm at $\sim215^{\circ}C(T_{2})$, and a high temperature endotherm at $\sim240^{\circ}C(T_{3})$. The drawn film of the nylon 6/ layered silicate nanocomposite was comprised of a mixture of the $\alpha and \gamma$ forms, with $the \alpha form$ being generated by drawing the pressed film having $the \gamma form$. The melting and crystallization of the crystals were observed at the above thermal transitions during the heating experiment performed at the Pohang X-ray synchrotron radiation source (4C2). The newly generated form was meta-stable and melted $at {\sim}T_{1}$. The double-melting $at {\sim}T_{2}$ was due to the exothermic crystallization of $the \alpha form$ during the main endothermic melting of $the \gamma form$. $The \alpha form$ crystallized $at {\sim}T_{2}$ and melted $at {\sim}T_{3}$.

• 대한화학회지
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• 제23권2호
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• pp.88-93
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• 1979

구리(Ⅱ)를 이온교환한 제올라이트 Y에서 프로필렌의 흡착을 부피법, 온도상승에 따른 탈착법 및 전자스핀공명스펙트럼을 사용하여 검토하였다. 프로필렌의 흡착량은 구리이온의 교환도가 증가함에 따라 증가하였다. 흡착된 상태는 최소한 4가지로서 $6.4^{\circ}C$/min으로 온도를 상승시켰을 때 탈착온도가 $108^{\circ}C({\alpha})$ , $243^{\circ}C({\beta})$, $284^{\circ}C({\gamma})$ 및 $420^{\circ}C({\delta})$ 였다. 이중 ${\alpha}$피이크는 제올라이트 격자내에 흡착된 것이었고, ${\beta}$ 및 ${\gamma}$는 구리 이온과 구리 이온에 의해 생성될 수 있는 Br$\"{o}$nsted 산점에 의해 흡착된 것이라고 생각되며 ${\delta}$피이크는 Br$\"{o}$nsted 산점에 의한 프로필렌의 중합체의 분해물이라고 생각된다.

• 한국결정성장학회지
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• 제9권1호
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• pp.113-118
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• 1999

$AlCl_3{\cdot}6H_2O$를 출발원료로 침전법에 의해 알루미늄 수화물을 합성하였다. 용액의 pH에 따라 amorphous, boehimite, bayerite, nordstrandite 상을 얻었고, 수산화 알루미늄은 열처리 온도가 증가함에 따라 $\gamma$, $\delta$, $\theta$를 거쳐${\alpha}-Al_2O_3$로 전이되었으며, 입자크기도 증가하였다. ${\gamma}-Al_2O_3$ 를 담금피막법(dip-coating method)으로 중간층 위에 코팅하였고, 비교를 위해 비지지체 분리막도 준비하였다. 지지체 분리막은 작은 입자(grain)들로 구성된 다공질 구조(porous structure)를 나타내었지만, 비지지체 분리막에서는 상호 연결된 큰 입자(grain)들이 나타났다. 지지체 분리막에서 보다 비지지체 분리막에서 결정립 성장이 명백하게 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.106-110
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• 2001

Formation of stoichiometric lithium-, nickel-, and zinc- ferrites by calcining organo-metallic precursors a temperature below 40$0^{\circ}C$ is examined using DTA/TG, and XRD techniques. It attempts to simulate th immobilization of metal ions in industrial liquid influents (waste) through the synthesis of stoichiometric spinel ferrites (SSF). Two steps of the SSF formation during thermal treatments are noted. The transformation of magnetite to ${\gamma}$ - Fe$_2$O$_3$and subsequent first formation of SSF were observed at temperatures ranging from 200 to 45$0^{\circ}C$. Th formation of cation-containing ${\gamma}$-Fe$_2$O$_3$and subsequent second formation of the ferrite occurred at temperature ranges of < 45$0^{\circ}C$ and 500 to $650^{\circ}C$, depending on the heating rate used. Then the temperature range of 200t 45$0^{\circ}C$ is critical to the performance of the technique, because a calcination at the range would lead to a complete formation of SSF, avoiding the occurrences of ${\gamma}$-Fe$_2$O$_3$and ion-containing ${\gamma}$-Fe$_2$O$_3$. If not, so $\alpha$-Fe$_2$O$_3$would occur. And annealing at temperature above $650^{\circ}C$ must be employed by which solid-state reactio of $\alpha$-Fe$_2$O$_3$with metal ions (possibly metal oxides) to form SSF can be conducted.

• 약학회지
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• 제37권5호
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• pp.511-519
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• 1993

The short and variabke transit of drug throught GI tracj and the inter-and intra-subject variations of the transit restrict the sustained drug absorption after oral adminstration. These restrictions may be solved by retaining the dosage forms in the stomach. Then the dosage form will act as a platform which releases the drug slowly and makes the GI absorption occur for a long time. In this study, as the platforms, PVP hydrogels were synthesized by chemical and y-irradiation method in the cylindrical test tube. The chemical method means the synthesis of the hydrogel by heating the mixed solution of N-vinyl-2-pyrrolidone [monomer], acrylated albumin [crosslinking agent], 2, 2'-agobis(2-methylpropionitrile) [initiator] and proxyphylline [drug] at $65^{\circ}C$ for 5 hr. The $\gamma$-irradiation method means the synthesis of the hydrogel by irradiation with $^{60}$ Co $\gamma$-ray of the mixed solution of the monomer, acrylated albumin, and flurbiprofen [drug] at room temperature with total 0.2 Mrad for 3 hr. Our intention is to design the hydrogel tablet (diameter : 1.20 cm, thickness : 0.60 cm) which swells in the gastric fluid after oral administration to such a size that passing through the pylorus could be inhibited during the period of drug release. After releasing drug, the hydrogel should be degraded by the enzymeatic digestion in the stomach, or by hydrolysis and eventually solubilized. Thus, in votro tests were performed to examine the factors that affect swelling and drug release from the PVP hydrogels. Experimental results show that the hydrogels swell to a size larger than the diameter of the pylorus(l.3$\pm$0.7 cm) and the hydrogel prepared by the chemical method is digested by pepsin. But the hydrogel prepared by the $\gamma$-irradiation method was not digested by the pepsin and just collapsed with time. Thus, the swelling of the hydrogel synthesized by $\gamma$-irradiation was independent albumin acrylation time and pepsin concentration. But drug content and radiation dose affected the swelling and drug release kinetics of the hydrogel. Drug release from the hydrigels was prolonged up to about 24 hr. Therefore, it was concluded that by adjusting these factors, the albumin-crosslinked PVP hydrogel synthesized by $\gamma$-irradiation method is expected to be retained in the stomach for up to 60hr and be a potential platform of drugs for long-term GI absorption.

• 한국표면공학회지
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• 제28권5호
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• pp.320-328
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• 1995

The electroplated steel sheets were heated during the short periods(10~60 seconds) at high temperature ($360^{\circ}C$～$500^{\circ}C$) in order to investigate thermal diffusion behaviors. When the steel sheets were heated for 10 seconds, all the coated layers were alloyed at $420^{\circ}C$ but at temperature lower than $400^{\circ}C$ the $\eta$ phase partially remained on the coated surface. At higher temperature, the longer the time for heat treatment the iron contents were increased in coated layer but the glossiness and whiteness of the coated surface were decreased. While the alloying phases of $\eta$, $\zeta$, $\delta_1$ and $\Gamma$ were appeared in the coated layer at the heat treatment temperature of $360^{\circ}C$, the phase was disappeared at $420^{\circ}C$ but the rests grew in size at the temperature of $440^{\circ}C$. When the heat treatment temperature and heating time were increased, the thickness of $\Gamma$ phase was rapidly increased to 0.8 $\mu\textrm{m}$. The optimum conditions for the heat treatment to prevent powdering of coated layer were obtained to heat it for 30 seconds at $400^{\circ}C$ and 10 seconds at $440^{\circ}C$, and the iron content in coated layer was suited to be 10 percents.

• 열처리공학회지
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• 제29권2호
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• pp.51-55
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• 2016

The P/M processing of titanium aluminide using amorphous TiAl is developed by which it is possible to overcome inherent fabricability problems and to obtain a fine microstructure. A high quality amorphous TiAl powder produced by reaction ball milling shows clear glass transition far below a temperature at the onset of crystallization in differential scanning calorimetry above a heating rate of 0.05 K/s. We obtained a fully dense compact of amorphous TiAl powders, encapsulated in a vacuumed can, via viscous flow by hot isostatic pressing (HIP). Isothermally annealing of HIP'ed amorphous compact under a pressure of 196 MPa shows a progressive growth of ${\gamma}-TiAl$ phase with ${\alpha}2$ ($Ti_3Al$), which is characterized by increasing sharpness of X-ray peaks with temperature. Fully dense HIP'ed compact of titanium aluminide TiAl shows a high hardness of 505 Hv, suggesting strengthening mechanisms by sub-micron sized grain of ${\gamma}-TiAl$ and particle-dispersion by second phase constituent, ${\alpha}2$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문
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• pp.73-80
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• 1996

Commerical purity aluminium , copper and STS 304 stainless steel sheets are welded by ultrasonic welding. The microstructures, x-ray diffraction profiles of planes , pole figures of the surface of original metal sheets are compared with those of the weld interface. The microstructures show disturbance and dark areas in the weld interface and grain refinement in the vicinity of the interface. The x-ray diffraction intensity of each plane in weld interface decreased in all metal sheets with exception of 9200) in steel sheet. The microstructure and x-ray diffraction intensity is affected by the mixture of deformation, heating and vibratin duringthe ultrasonic welding. Therefore, after the ultrasonic welding, the positions of the peak intensity in the pole figures are changed, the value of the maximum pole intensity is decreased in Al, is increased in copper and stainless steel. Very strong {100} <001> texture, strong {100} <001>,{123}<634> textures in original Al surface are transformed into weak, {100}<001>, {110}<112> and {112}<111> components in weld surface, weak (110) fiber is slightly changed to (110) fiber in copper, (100)and ${\gamma}$ fiber components are transformed into strong ${\gamma}$ fiber component in stainless steel.