• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.815-820
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• 2014

We applied the two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 2,4-difluorophenol. As supported by our theoretical calculations, only the cis form of 2,4-difluorophenol involves in the two-photon photoexcitation and pulsed field ionization processes. The band origin of the $S_1{\leftarrow}S_0$ electronic transition of cis-2,4-difluorophenol appears at 35 647 ${\pm}2cm^{-1}$ and the adiabatic ionization energy is determined to be 70 $030{\pm}5cm^{-1}$, respectively. Most of the observed active vibrations in the electronically excited $S_1$ and cationic ground $D_0$ states mainly involve in-plane ring deformation vibrations. Comparing these data of cis-2,4-difluorophenol with those of phenol, cis-2-fluorophenol, and 4-fluorophenol, we found that there is an additivity rule associated with the energy shift resulting from the additional fluorine substitution.

• 생약학회지
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• 제8권1호
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• pp.17-21
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• 1977

$^{13}C-NMR$ behaviors of phenolic compounds such as phenol, catechol, pyrogallol, resorcine, phoroglucine and hydroquinone were studied. From the study on the effects of OH-substitution on benzene and its dervatives it was found that the additivity rule can be applied to the ortho-and para-effect but not to the meta-effect for the OH-function. The empirically calculated chemical shifts regarding the o-and p-effects coincide very well with the results of measurement. The chemical shifts of the phenolic compounds can be classified into three types. 1) Catechol-type C-1 and C-2 145 ppm C-3 and C-6 116-107 ppm 2) Pyrogallol-type C-1 132ppm C-2 and C-6 146ppm C-3 and C-5 106ppm 3) Resorcin-type C-1 and C-3 159ppm C-2 103-95ppm C-4 and C-6 107ppm

• Journal of Welding and Joining
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• 제18권5호
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• pp.55-62
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• 2000

A metallurgical model for the phase transformation kinetics at Coarsened Grain Heat Affected Zone(CGHAZ) on the basis of Johnson-Mehl-Avrami equation(JMA equation) was proposed. In this model, the effect of prior austenite grain size on the transformation and the morphological changes of ferrite were considered. Isothermal dilatometer tests were performed to determine the effect of prior austenite grain size (AGS) on the austenite decomposition to ferrite and pearlite in a plain carbon steel. By comparing the calculated volume fraction with measured data, the reliability of the developed model was discussed.

• 열처리공학회지
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• 제32권1호
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• pp.17-28
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• 2019

Jominy hardenability curves of low alloy steel containing less than 5 wt.% of alloying elements in total were calculated by applying Scheil's rule of additivity to pre-calculated isothermal transformation curve. Isothermal transformation curve for each phase in steel was approximated as a simple mathematical equation by using Kirkaldy's approach and all coefficients in the equation were estimated from experimental temperature-time-transformation (TTT) and/or continuous cooling transformation (CCT) data in the literature. Then jominy test with simple boundary conditions was performed in computer by applying the finite difference scheme. The resultant cooling curves at each location along a longitudinal direction of Jominy bar were applied to calculate phase fractions as well as mechanical properties such as micro Vickers hardness. The simulated results were compared with experimental CCT data and Jominy curves in the literature.

• Fibers and Polymers
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• 제7권4호
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• pp.358-366
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• 2006

Thermotropic liquid crystal polymer (TLCP)-reinforced poly(butylene terephthalate) (PBT) composites were prepared by melt processing. The improvement in the mechanical properties and the processability of the PBT/TLCP composites was attributed to the reinforcing effect by TLCP phase and its well distribution in the PBT matrix. X-ray diffraction results demonstrated that a slow cooling process leads to the thicker lamellar structures and the formation of more regular crystallites in the composites. The incorporation of TLCP improves not only the tensile strength and flexural modulus but also the heat distortion temperature (HDT) of the PBT/TLCP composites. The HDT values of the composites were dependent on TLCP content. The improvement in the HDT values of the PBT/TLCP composites may be explained in terms with the increased flexural modulus, the development of more regular crystalline structures, and the enhancement of the ability of the composites to sustain the storage modulus by TLCP phase. In addition, the simple additivity rule makes it possible to predict the HDT values of the PBT/TLCP composites.

• Journal of Welding and Joining
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• 제25권2호
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• pp.62-69
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• 2007

A kinetic model fur the particle coarsening behavior was developed. The proposed model considered the critical particle size which can be derived from Gibbs-Thomson equation unlike the conventional approach. In this study, the proposed particle coarsening model was applied to study the coarsening behavior of titanium nitride (TiN particle) in microalloyed steel weld HAZ. Particle size distributions and mean particle size by the proposed model were in agreement with the experimental results. Meanwhile, using additivity rule, the isothermal model was extended to predict particle coarsening behavior during continuous thermal cycle.

• Journal of Welding and Joining
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• 제24권4호
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• pp.39-49
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• 2006

The austenite grain growth model in low alloyed steel HAZ without precipitates was proposed by analyzing isothermal grain growth behavior. Steels used in this study were designed to investigate the effect of alloying elements. Meanwhile, a systematic procedure was proposed to prevent inappropriate neglect of initial grain size (D0) and misreading both time exponent and activation energy for isothermal grain growth. It was found that the time exponent was almost constant, irrespectively of temperature and alloying elements, and activation energy increased with the addition of alloying elements. From quantification of the effect of alloying elements on the activation energy, an isothermal grain growth model was presented. Finally, combining with the additivity rule, the austenite grain size in the CGHAZ was predicted.

• 공업화학
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• 제3권4호
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• pp.614-619
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• 1992

Soft segment가 각각 ester 및 ether형 polyol로된 2종의 polyurethane(PU) ionomer를 emulsion 블렌딩하여, 블렌드의 분산점도, 및 emulsion cast film의 접촉각, 기계적 특성을 조성의 함수로 측정하였다. 블렌드의 기계물성은 혼합법칙으로부터 심한 scattering이나, negative deviation을 보였으며, 이는 ester 및 ether형 polyol간의 상용성의 결여에 기인하는 것으로 보았다. 접촉각 측정 결과로부터 유화입경이 작은 PPG PU 입자가 주로 도막표면층을 형성하는 것을 확인할 수 있었다.

• 한국세라믹학회지
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• 제40권4호
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• pp.354-359
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• 2003

The microwave dielectric characteristics of (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ (0$\leq$x$\leq$1.0) ceramics were investigated by crystalstructure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ transformed to tetragonal structure. Because the ionic radius of (Mg$\_$1/3/Ta$\_$2/3/)$\^$4+/was slightly bigger than one of (Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)$\^$4+/, the cell parameters increased with increase of (Mg$\_$1/3/Ta$\_$2/3/)O$_2$concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the a. Though the grain size increased, however, the porosity deteriorated the q. Therefore, the a depended on the order/disorder, the porosity, and the grain size in regular order.

• Journal of Welding and Joining
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• 제28권3호
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• pp.104-113
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• 2010

In this study, to predict the microstructure in weld HAZ of low alloyed steel, prediction model for the phase transformation considering the influence of prior austenite grain size and cooling rate was developed. For this study, six low alloyed steels were designed and the effect of alloying elements was also investigated. In order to develop the prediction model for ferrite transformation, isothermal ferrite transformation behaviors were analyzed by dilatometer system and 'Avrami equation' which was modified to consider the effect of prior austenite grain size. After that, model for ferrite phase transformation during continuous cooling was proposed based on the isothermal ferrite transformation model through applying the 'Additivity rule'. Also, start temperatures of ferrite transformation were predicted by $A_{r3}$ considering the cooling rate. CCT diagram was calculated through this model, these results were in good agreement with the experimental results. After ferrite transformation, bainite transformation was predicted using Esaka model which corresponded most closely to the experimental results among various models. The start temperatures of bainite transformation were determined using K. J. Lee model. Phase fraction of martensite was obtained according to phase fractions of ferrite and bainite.