• 한국세라믹학회지
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• 제11권2호
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• pp.22-30
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• 1974

This study was carried out to investigate the species of iron compounds in kaolin mineral and the bonding relation between the major kaolin and its subordinate iron compound existing as incidental mineral in common clay by means of chemical composition, X-ray diffraction, thermal differential and thermogravimetrie analysis for the application of clays in the field of ceramic raw material. The domestic clay are produced abounduntly in many places, but San-Cheong kaolin, Chu-An clay, and Yeong-Am clay were selected as samples in this experiment because of their frequent utilization in porcelain industry. Two kinds of samples with low and high iron content are picked up respectively from the place of production and elutriated under two micron size to determine the properties and concentration of iron compound very fine particles or colloidal substance of low crystalline grade. Therefore, hydrothermal treatment in autoclave was conducted considering the existence of low crystalline grade of iron compounds known as an amorphoue state in X-ray diffraction pattern furthermore, de-iron treatment of hydrothermal compound was done in order to identify the related iron compound before and after hydrothermal reaction and iron compound which is one of the samples was synthesized for the determination of their compounds state in more detail. The obtained results in this study are as follows: In San-Cheong kaolin, Chu-An clay and Yeong-Am clay 1) It is proved that species accompanying iron compound is $\alpha$-FeOOH form. 2) Iron compound is composed of very fine particles or colloidal substance. 3) The iron substance encircles the fine parts of clay minerals under 2 micron and acts as cementizing agent.

• 한국진공학회지
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• 제7권1호
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• pp.11-16
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• 1998

본 연구에서는 GaAs의 selenium보호막형성 효과를 관찰하기 위하여 $Na_2$Se/NH$_4$OH 용액을 제조하고 X-선 광전자 분광기(X-ray photoelectron spectroscopy)와 photoluminescence(PL)를 이용하여 표면처리된 GaAs의 처리직후 및 대기중 노출에 따른 화학적 결합특성 및 광학적 특성을 관찰하였다. 용액처리 직후, 표면에는 As-Se결합이 형성 되었으며 Se는 한가지 산화상태인 -2가로 존재함이 관찰되었다. 또한 세정처리후의 표면보 다 Se용액처리 이후에 PL의 피이크 세기가 크게 증가됨으로부터 Se 용액처리가 GaAs의 표면상태밀도를 효과적으로 감소시킬 수 있음을 확인할 수 있었다. 그러나 처리 직후 공기 중 노출없이 관찰한 GaAs표면에서 산화막이 국부적으로 관찰되었으며 이렇게 처리과정중 생성된 산화막은 대기중 노출에 따라 산화막 성장을 유도하고 표면처리 효과를 저하시키는 주요인으로 작용함을 알 수 있었다. 이는 Se용액처리된 GaAs표면의 PL강도가 대기중 노출 에 따라 감소하며 세정처리후 GaAs표면의 PL강도와 유사한 값을 나타냄으로 부터도 확인 할 수 있었다.

• Elastomers and Composites
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• 제49권1호
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• pp.24-30
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• 2014

3-Amino-1,2,4-triazole(ATA)을 비상용성 블렌드인 maleated HDPE(mHDPE)/maleated EPDM (mEPDM)(50 wt%/50 wt%)에 용융혼합에 의해 2.5 phr, 5.0 phr 첨가하였으며, ATA 첨가에 따른 블렌드의 미세구조, 기계적물성 및 유변물성을 FT-IR, FE-SEM, 인장시험, DMA 및 ARES를 이용하여 각각 조사하였다. FTIR 및 DMA 분석결과 용융혼합 과정에서 ATA가 mHDPE 및 mEPDM의 말레무수물과 반응하여 초분자적 수소결합이 형성되며, 이로부터 물리적 가교구조가 형성되는 것을 알 수 있었다. FE-SEM 분석결과 mHDPE/mEPDM 블렌드는 플라스틱인 HDPE가 연속상을 이루고 고무상인 EPDM이 분산상을 이루며 ATA를 첨가함으로써 모폴로지가 더욱 미세해짐을 알 수 있었다. 인장물성시험결과 ATA에 첨가에 의해 형성된 물리적가교구조로 인해 인장강도, 모듈러스, 파단신율 값 및 탄성복원력이 증가되었으며, 용융레올로지 특성 분석결과 ATA가 첨가됨으로써 블렌드의 저장탄성율과 용융점도가 증가됨을 알 수 있었다.

• 대한화학회지
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• 제23권6호
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• pp.339-348
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• 1979

물-메탄올, 물-에탄올, 물-아세트니틜, 물-아세톤 및 아세트니트릴-메탄올의 2성분 혼합용매에서 2-염화테노일 및 2-염화퓨로일의 가용매분해 반응을 속도론적으로 연구하였다. 반응 속도는 반양성자성 용매에서 보다 양성자성 용매에서 더 빨랐으며 이것은 양성자성용매의 수소결합능력이 이탈기의 결합의 파괴를 돕기 때문이다. 그러나 아세트니트릴-메탄올 혼합용매에서는 특수용매화가 일어나며, 메탄올 몰분율 0.8부근에서 최대속도를 나타낸다. 또한 이 반응은 염화벤조일보다 느리며 그 속도 순서는 염화벤조일 > 2-염화테노일 > 2-염화퓨로일이며 이 중에서 퓨란고리의 전자흡인성이 제일 강함으로 전이상태에서 결합의 파괴가 어려워져서 반응속도가 늦어지는 것이다. 반응메카니즘은 전이상태에서 결합의 파괴가 결합의 형성보다 많이 진행된 dissociative $S_N2$ 반응이기는 하나 2-염화테노일은 물 함량이 많은 부분에서는 $S_N1$ 성겨기 꽤 크고 $S_N2$ 성격이 약화된다.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2448-2452
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• 2014

Second-order rate constants ($k_N$) have been measured spectrophotometrically for $S_NAr$ reactions of Y-substituted-phenoxy-2,4-dinitrobenzenes (1a-1g) with hydrazine and glycylglycine in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Hydrazine is 14.6-23.4 times more reactive than glycylglycine. The magnitude of the ${\alpha}$-effect increases linearly as the substituent Y becomes a stronger electron-withdrawing group (EWG). The Br${\o}$nsted-type plots for the reactions with hydrazine and glycylglycine are linear with ${\beta}_{lg}=-0.21$ and -0.14, respectively, which is typical for reactions reported previously to proceed through a stepwise mechanism with expulsion of the leaving group occurring after rate-determining step (RDS). The Hammett plots correlated with ${\sigma}^{\circ}$ constants result in much better linear correlations than ${\sigma}^-$ constants, indicating that expulsion of the leaving group is not advanced in the transition state (TS). The reaction of 1a-1g with hydrazine has been proposed to proceed through a five-membered cyclic intermediate ($T_{III}$), which is structurally not possible for the reaction with glycylglycine. Stabilization of the intermediate $T_{III}$ through intramolecular H-bonding interaction has been suggested as an origin of the ${\alpha}$-effect exhibited by hydrazine.

• Tribology and Lubricants
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• 제32권5호
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• pp.141-146
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• 2016

The diketopyrrolopyrrole (DPP) pigment is a bicyclic 8-π-electron system containing two lactam units. Typical DPP derivative pigments have melting points of over 350°C and very low solubility in most solvents, and show absorption in the visible region with a molar extinction coefficient of 33,000 dm²mol⁻¹ and strong photoluminescence with maxima in the range 500–600 nm. X-ray structure analyses of DPP show that the whole molecule is almost in one plane. The phenyl rings are twisted out of the heterocyclic plane and the intermolecular hydrogen bonding between neighboring lactam NH and carbonyl units influences the structure of the DPP pigment in the solid state. In this study, mono-N-alkylation and mono-N-arylation were undertaken for Pigment Red 264 or Pigment Orange 73 with alkyl halide and aryl halide, respectively, in the presence of sodium tert-butoxide as a base catalyst to improve the solubility of DPP pigments and their application as CO₂ indicators. The synthetic yield was in the range 11–88%. The indicator dyes are highly soluble in organic solvents and shows pH-dependent absorption (λ_max 501 and 572 nm for the protonated and deprotonated forms, respectively) and emission (λ_max 524 and 605 nm for the protonated and deprotonated forms, respectively) spectra. The mono-N-alkylated and mono-N-arylated DPP pigment was identified by ¹H-NMR (¹H-Nuclear Magnetic Resonance Spectrometer), FT-IR (Fourier Transform Infrared Spectroscopy), and MS (Mass Spectrometry). According to the results of color and hue properties obtained by a color matching analyzer, the synthesized DPP pigment material can be used as a CO₂ indicator.

• 대한화학회지
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• 제50권4호
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• pp.291-297
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• 2006

Cyclopropyl 링과 할로겐 원소가 결합된 붕소원자 사이의 hyperconjugation 효과를 알아보기 위하여 CPDFB와 CPCFB 분자의 여러 conformation과 transition state 구조들에 대해 DFT와 ab initio 방법을 사용하여 다양한 레벨에서 구조최적화 및 NBO 분석을 수행하였다. 그 결과 주요 상호작용 형태는 화합물에 따라 단일결합 오비탈 (C1-C3, C2-C3) n* (B9) 또는 *(B9-Cl11) 오비탈로 전자를 제공하는 것이었고 이때 안정화 에너지는 CPDFB 분자의 경우 6.63 kcal/mol, CPCFB 분자의 경우는 conformation에 따라 6.97(E-form)/6.79(Z-form) kcal/mol 이었다. 또한, BF2와 BFCl 기의 내부회전에 의한 회전장벽의 크기는 각각 5.3~6.7 kcal/mol과 5.7~6.5 kcal/mol로 기존에 보고된 실험값과 잘 일치함을 보였다. 마지막으로 CPCFB 분자의 conformers 중에서 Z-form이 global minimum으로 확인되었고 E-form 보다 0.2 kcal/mol 정도 안정하였다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2923-2928
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• 2010

This study examined the synthesis of the crystal structure of bis(2,2'-bipyridine)nitrato zinc (II) nitrate, $[Zn(bipy)_2(NO_3)]^+NO_3^-$ using a microwave treatment at 300 W and 60 Hz for the application to dye-sensitized solar cells. The simulated complex structure of the complex was optimized with the density functional theory calculations for the UV-vis spectrum of the ground state using Gaussian 03 at the B3LYP/LANL2DZ level. The structure of the acquired complex was expected a penta-coordination with four nitrogen atoms of bipyridine and the oxygen bond of the $NO_3^-$ ion. The reflectance UV-vis absorption spectra exhibited two absorptions (L-L transfers) that were assigned to the transfers from the ligand ($\sigma$, $\pi$) of $NO_3$ to the ligand ($\sigma^*$, $\pi^*$) of pyridine at around 200 - 350 nm, and from the non-bonding orbital (n) of O in $NO_3$ to the p-orbital of pyridine at around 450 - 550 nm, respectively. The photoelectric efficiency was approximately 0.397% in the dye-sensitized solar cells with the nanometer-sized $TiO_2$ at an open-circuit voltage (Voc) of 0.39 V, a short-circuit current density (Jsc) of $1.79\;mA/cm^2$, and an incident light intensity of $100\;mW/cm^2$.

• 대한화학회지
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• 제37권4호
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• pp.408-415
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• 1993

$CH_4,\;CH_3F,\;CH_2F_2,\;CHF_3$ 과 $NH_3$ 및 H_2O$와의 수소결합 이량체들에 대하여 9s5p/5s 및 9s5p1d/5s1p의 basis sets를 사용하여 체계적인 ab initio 계산을 하였다. 이들 이량체들의 바닥상태성질을 구하여 독립된 단위체들의 대응하는 성질과 비교하였으며, 평형기하구조, 안정화에너지, 쌍극자모멘트 및 분자간 결합의 힘상수 등을 보고하였다. 사슬형 소중합체들에서 수소결합의 비가감적 거동의 결과로부터 일어나는 여러가지 효과들을 논의하고, SCF 근사법의 사용에 따른 체계적 및 조직적인 오차들과 계산결과들의 basis sets 의존성을 지적하였다.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.214-218
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• 2009

Second-order rate constants ($k_N$) have been measured for nucleophilic substitution reactions of S-4-nitrophenyl thiobenzoate with a series of alicyclic secondary amines in $H_2O$ containing 20 mol % DMSO at 25.0 ${\pm}$ 0.1 ${^{\circ}C}$. The Br$\phi$nsted-type plot exhibits a downward curvature, i.e., $\beta_{nuc}$ decreases from 0.94 to 0.34 as the amine basicity increases. The reactions in the aqueous DMSO have also been suggested to proceed through a zwitterionic tetrahedral intermediate (T${\pm}$) with change in the RDS on the basis of the curved Br$\phi$nsted-type plot. The reactions in the aqueous DMSO exhibit larger $k_N$ values than those in the aqueous EtOH. The macroscopic rate constants ($k_N$) for the reactions in the two solvent systems have been dissected into the microscopic rate constants ($k_1\;and\;k_2/k_{-1}$ ratio) to investigate effect of medium on reactivity in the microscopic level. It has been found that the $k_2/k_{-1}$ ratios are similar for the reactions in the two solvent systems, while $k_1$ values are larger for the reactions in 20 mol % DMSO than for those in 44 wt % EtOH, indicating that the larger $k_1$ is mainly responsible for the larger $k_N$. It has been suggested that the transition state is more stabilized in 20 mol % DMSO through mutual polarizability interaction than in 44 wt % EtOH through H-bonding interaction.