• 대한화학회지
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• 제31권2호
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• pp.197-202
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• 1987

cis 및 trans 2-methyl-N-phenyl-1,3-oxathiolane-2-acetamide (b) 및 (c)의 sigmatropic rearrangement에 의하여 생성되는 각각의 sulfenic acid (d) 및 (f)는 deuterium exchange reaction에 의하여 확인되었다. cis와 sulfoxide (b)와 (c)의 이성질화가 중성조건하에서는 일어나지 않으나, 산성촉매 존재하에서는 일어난다는 것이 발견되었다. 중성조건하에서 이성질화가 일어나지 않는 것은 sulfenic acid의 SOH 산소원자와 NH proton 사이의 수소결합이 관여하는 stereospecific recyclization에 기인하거나 기하학적 요구에 기인한다고 설명된다. 한편 cis sulfoxide (b)와 trans sulfoxide (c)의 혼합물을 주는 전구물질 1, 3-oxathiolane의 산화반응에서 benzene seleninic acid를 촉매로 하는 $H_2O_2$의 산화에 의하여 cis sulfoxide (b)가 높은 수율로 선택적으로 얻어졌다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.202-202
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• 1999

The Polyethylene (PE), Polystyrene (PS) and Polytetrafluoroethylene (PTFE) surface modification was investigated by hydrogen io assisted reaction (H-IAR) in oxygen environment. The IAR is a kind of surface modification techniques using ion beam irradiation in reactive gas environment. The energy of hydrogen ion beam was fixed at 1keV, io dose was varied from 5$\times$1014 to 1$\times$1017 ions/$\textrm{cm}^2$, and amount of oxygen blowing gas was fixed 4ml/min. Wettability was measured by water contact angles measurement, and the surface functionality was analyzed by x-ray photoelectron spectroscopy. The contact angle of water on PE modified by argon ion beam only decrease from 95$^{\circ}$ to 52$^{\circ}$, and surface energy was not changed significantly. But, the contact angle using hydrogen ion beam with flowing 4ml/min oxygen stiffly decreased to 8$^{\circ}$ and surface energy to 65 ergs/cm. In case of PS, the contact angle and surface energy changes were similar results of PE, but the contact angle of PTEE samples decreased with ion dose up to 1$\times$1015 ions/$\textrm{cm}^2$, increased at higher dose, and finally increased to the extent that no wetting was appeared at 1$\times$1017 ions/$\textrm{cm}^2$. These results must be due to the hydrogen ion beam that cleans the surface removing the impurities on polymer surfaces, then hydrogen ion beam was activated with C-H bonding to make some functional groups in order to react with the oxygen gases. Finally, unstable polymer surface can be changed from hydrophobic to hydrophilic formation such as C-O and C=O that were confirmed by the XPS analysis, conclusionally, the ion assisted reaction is very effective tools to attach reactive ion species to form functional groups on C-C bond chains of PE, PS and PTFE.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4514-4521
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• 2022

In this study, the effects of heat and radiation on the degradation behaviour of fluoroelastomer under simulated normal operation and a severe accident environment were investigated using sequential testing of gamma irradiation and thermal degradation. Tensile properties and Shore A hardness were measured, and thermogravimetric analysis was used to evaluate the degradation behaviour of fluoroelastomer. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the structural changes of the fluoroelastomer. Heat and radiation generated in nuclear power plant break and deform the chemical bonds, and fluoroelastomer exposed to these environments have decreased C-H and functional groups that contain oxygen and double bonds such as C-O, C=O and C=C were generated. These functional groups were formed by auto oxidation by reacting free radicals generated from the cleaved bond with oxygen in the atmosphere. In this auto oxidation reaction, crosslinks were generated where bonded to each other, and the mobility of molecules was decreased, and as a result, the fluoroelastomer was hardened. This hardening behaviour occurred more significantly in the severe accident environment than in the normal operation condition, and it was found that thermal stability decreased with the generation of unstable structures by crosslinking.

• 한국염색가공학회지
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• 제22권2호
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• pp.132-139
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• 2010

Sericin pulverization process was applied by freezing-thawing of sericin protein concentration solution and physicochemical properties of sericin/chitosan blended films were investigated. In sericin pulverization process by freezing-thawing method, the refrigeration storage at $4^{\circ}C$ maximized gelling between sericin molecules, which increased 10% of recovery ratio from sericin concentration solution that using ultrafiltration procedure. In physicochemical properties of sericin/chitosan blended films, the maximum load of chitosan (6.7kgf) had higher than that of sericin (1.2kgf), and the elongation of sericin and chitosan had 96% and 34%, respectively. Also FT-IR analysis of sericin/chitosan blended films showed that both sericin and chitosan films had amide I peak (N-H bond) in $1,521cm^{-1}$ and amide II peak (C=O bond) in $1,630cm^{-1}$. In addition, it could confirm compatibility between both materials as indicated by the decrease in the amide I peak's absorption value as chitosan content increases.

• Elastomers and Composites
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• 제54권2호
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• pp.110-117
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• 2019

The characterization of the ozone oxidation for raw natural rubber (NR) was investigated under controlled conditions through image and fourier transform infrared (FT-IR) analysis. The ozone oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at $40^{\circ}C$ under low humidity conditions to completely exclude thermal, moisture, or light oxidation. The ozone concentration was set at 40 parts per hundred million (pphm). Before or after exposure to ozone, the image of the thin film for raw NR was observed at a right or tilted angle. FT-IR absorption spectra were measured in the transmission mode according to ozone exposure time. The ozone oxidation of NR was determined by the changes in the absorption peaks at 1736, 1715, 1697, and $833cm^{-1}$, which were assigned to an aldehyde group (-CHO), a ketone group (-COR), an inter-hydrogen bond between carbonyl group (-C=O) from an aldehyde or a ketone and an amide group (-CONH-) of protein, and a cis-methine group ($is-CCH_3=CH-$, respectively. During ozone exposure period, the results indicated that the formation of the carbonyl group of aldehyde or ketone was directly related to the decrement of the double bond of cis-1,4-polyisoprene. Only carbonyl compounds such as aldehydes or ketones seemed to be formed through chain scission by ozone. Long thin cracks with one orientation at regular intervals, which resulted in consecutive chain scission, were observed by image analysis. Therefore, one possible two-step mechanism for the formation of aldehyde and ketone was suggested.

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2955-2959
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• 2011

Second-order rate constants for nucleophilic substitution reactions of 2,4-dinitrophenyl benzenesulfonate 1a with a series of alicyclic secondary amines in MeCN have been measured spectrophotometrically and compared with those reported previously for the corresponding reactions performed in aqueous medium to investigate the effect of medium on reactivity and reaction mechanism. The amines employed in this study are found to be more reactive in the aprotic solvent than in $H_2O$. The reactions of 1a in MeCN result in a linear Br${\o}$nsted-type plot with ${\beta}_{nuc}$ = 0.58, which contrasts to the curved Br${\o}$nsted-type plot reported previously for the corresponding reactions performed in the aqueous medium (i.e., ${\beta}_2$ = 0.86 and ${\beta}_1$ = 0.38). Accordingly, it has been concluded that the reaction mechanism changes from a stepwise mechanism to a concerted pathway upon changing the medium from $H_2O$ to MeCN. Reactions of Y-substituted phenyl benzenesulfonates 1a-c with piperidine in MeCN result in a linear Br${\o}$nsted-type plot with ${\beta}_{lg}$ = -1.31, indicating that expulsion of the leaving group is significantly more advanced than bond formation in the transition state. The trigonal bipyramidal intermediate ($TBPy^{\pm}$) proposed previously for the reactions in $H_2O$ would be highly unstable in MeCN due to strong repulsion between the negative charge in $TBPy^{\pm}$ and the negative dipole end of MeCN. Thus, destabilization of $TBPy^{\pm}$ in MeCN has been concluded to change the reaction mechanism from a stepwise mechanism to a concerted pathway.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.116-119
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• 2003

Self-patterning of thin films using photosensitive sol solution has advantages such as simple manufacturing process compared to photoresist/dry etching process. In this study, ferroelectric $Sr_{0.9}Bi_{2.1}Ta_2O_9$(SBT) and $La_{0.5}Sr_{0.5}CoO_3$(LSCO)thin films have been prepared by spin coating method using photosensitive sol solution. $Sr(OC_2H5)_2$, $Bi(TMHD)_3$ and $Ta(OC_2H)_5)_5$ were used as starting materials for SBT solution and $La(OCH_2CH_2OCH_3)_3$, $Sr(OC_2H_5)_2$, $CO(OCH_2CH_2OCH_3)_2$ were used for LSCO solution. Solubility difference by UV irradiation on LSCO thin film allows to obtain a fine patterning due to M-O-M bond formation. The lowest resistivity($4{\times}10^{-3}{\Omega}cm$) of LSCO thin films was obtained by annealing at $740^{\circ}C$.

• 한국재료학회지
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• 제33권11호
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• pp.465-474
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• 2023

The effects of La³⁺ substitution for Sr²⁺-site on the crystal structure and the dielectric properties of (Ba_0.7Sr_0.3-3x/2La_x) (Ti_0.9Zr_0.1)O₃ (BSLTZ) (0.005 ≤ x ≤ 0.02) ceramics were investigated. The structural characteristics of the BSLTZ ceramics were quantitatively evaluated using the Rietveld refinement method from X-ray diffraction (XRD) data. For the specimens sintered at 1,550 ℃ for 6 h, a single phase with a perovskite structure and homogeneous microstructure were observed for the entire range of compositions. With increasing La³⁺ substitution (x), the unit cell volume decreased because the ionic size of La³⁺ (1.36 Å) ions is smaller than that of Sr²⁺ (1.44 Å) ions. With increasing La³⁺ substitution (x), the tetragonal phase fraction increased due to the A-site cation size mismatch effect. Dielectric constant (ε_r) increased with the La³⁺ substitution (x) due to the increase in tetragonality (c/a) and the average B-site bond valence of the ABO₃ perovskite. The BSLTZ ceramics showed a higher dielectric loss due to the smaller grain size than that of (Ba_0.7Sr_0.3)(Ti_0.9Zr_0.1)O₃ ceramics. BSLTZ (x = 0.02) ceramics met the X7R specification proposed by the Electronic Industries Association (EIA).

• 한국광물학회지
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• 제16권3호
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• pp.215-222
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• 2003

캐나다 퀘벡주 파커광산(Parker mine)에서 산출된 삼팔면체 운모인 금운모-1M 시료에 대하여 중성자분말회절 분석을 실시하고 리트벨트법을 통해 그 결정구조를 해석하였으며, 특히 X선 분말회절법으로는 해석이 어려운 금운모 구조 내의 OH기의 크기 및 길이, 그리고 방향성을 결정하였다. 연구에 이용된 금운모의 화학조성은 EPMA 분석결과 $K_2$(M $g_{4.46}$F $e_{0.83}$A $l_{0.34}$ $Ti_{0.22}$)(S $i_{5.51}$A $l_{2.49}$) $O_{20}$(O $H_{3.59}$ $F_{0.41}$)로 나타났다. 중성자 분말회절실험은 상온과 극저온(-263$^{\circ}C$)에서 실시하였으며, 회절값으로부터 구한 금운모의 단위포 상수는 a=5.30∼5.31 $\AA$, b=9.18∼9.20 $\AA$, c=10.18∼10.21 $\AA$, $\beta$=100.06∼100.08$^{\circ}$로 결정되었다. R지수의 경우 극저온(-263$^{\circ}C$)에서의 값이 $R_{p}$=2.35%, $R_{wp}$=3.01%로, 상온에서의 값( $R_{p}$=2.51%, $R_{wp}$=3.18%)보다 다소 적게 나타났는데, 이는 낮은 온도에서 온도인자 (B_iso)에 대한 영향이 적어짐에 따라 나타나는 결과로 생각된다. OH기의 결합거리는 상온에서 0.93 $\AA$, 저온에서 1.03 $\AA$, 방향성은 93.4$^{\circ}$∼93.6$^{\circ}$로 측정되었다 극저온에서 상온으로 온도가 상승하면서 OH기의 크기가 감소하는 것은 온도 상승에 따른 진동효과보다는 결정구조내의 수소결합과 관련있는 것으로 해석된다.석된다.석된다.으로 해석된다.석된다.석된다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.443-448
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• 2012

Ferrocenyl chalcones (Fc-C(O)CH=CH-Ar: Fc-Ar) with mono- and di-1-naphthalenyl moieties (Fc-1Naph and Fc-d1Naph) were prepared and spectroscopically characterized. The enone bridge was in the s-cis conformation and the $\pi$-electrons on the C=C bond were further delocalized on the bridge. The naphthalenyl moiety deviates greatly from the enone-Cp plane by $26.9(1)^{\circ}$. Cyclic voltammetry measurements for Fc-1Naph exhibit one reversible cycle for the redox of the ferrocenyl moiety at a lower potential, and one irreversible oxidation peak at the higher potential region. For Fc-d1Naph, the cyclic voltammogram is more featureless. Fluorescence properties for both compounds are active in polar solvents with $\lambda_{em}$ = 500 nm (EtOH) and $\lambda_{em}$ = 512 nm (MeOH) for Fc-1Naph and $\lambda_{em}$ = 496 nm (EtOH) and $\lambda_{em}$ = 508 nm (MeOH) for Fc-d1Naph. The intensity of Fc-d1Naph is more than twice than that of Fc-1Naph. The fluorescence properties for both compounds are inactive in the less polar solvents such as $CH_3CN$, $CH_2Cl_2$ and $CHCl_3$.