• 폴리머
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• 제36권6호
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• pp.739-744
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• 2012

본 연구에서는 합성한 styrene-acrylonitrile(SAN) 전구체를 기반으로 한 탄소를 제조하였다. 그 제조된 탄소는 화학적 환원법으로 활성화하였고, 그 활성화된 SAN 기반 탄소를 A-SAN이라 명명하였다. 전기이중층 커패시터의 전극용 A-SAN 기반 탄소의 표면 특성과 전기화학적 특성에 있어서 활성화 온도에 의한 효과를 확인하기 위해 다양한 온도에서 활성화를 진행하였다. A-SAN의 특성분석을 위해 X-선 회절분석법(XRD), 주사전자현미경(SEM) 그리고 비표면적 장치에 의해 조사되었다. 또한 전기화학적 거동은 순환전류전압과 정전류 충방전법으로 측정하였다. 그 실험 결과로부터, A-SAN 700이 우수한 전기화학적 특성과 가장 높은 비축전용량 값을 보였지만, 활성화 온도가 $700^{\circ}C$가 넘으면 이러한 특성들은 감소했다. 이것은 $700^{\circ}C$ 이상의 온도에서의 활성화가 마이크로 기공 구조의 변형을 야기하기 때문인 것으로 사료된다.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.73-78
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• 2006

In this paper, creep tests of Mg-Zn-Mn and Mg-Zn-Mn-Ca alloys, which were casted by mold with Mg-3%Zn-1%Mn and Mg-3%Zn-1%Mn-0.2%Ca, were done under the temperature range of 473-573K and the stress range of 23.42-78.00Mpa. The activation energies and the stress exponents were measured to investigate the creep plastic deformation of those alloys, and the rupture lifes of Mg-Zn-Mn alloy were also measured to investigate the fracture behavior. From the results, the activation energy of Mg-Zn-Mn and Mg-Zn-Mn-Ca alloys under the temperature range of 473-493K were measured as 149.87, 145.98KJ/mol, respectively, and the stress exponent were measured as 5.13, 6.06 respectively. Also the activation energies Mg-Zn-Mn and Mg-Zn-Mn-Ca alloys under the temperature range of 553-573K were obtained as 134.41, 129.22KJ/mol, respectively, and tress exponent were obtained as 3.48, 4.63, respectively. Finally stress dependence of rupture life and the activation energy of rupture life of Mg-Zn-Mn under the temperature range of 473-493K was measured as 8.05, 170.0(KJ/mol), respectively, which were a little higher than the results of steady state creep.

• 한국결정성장학회지
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• 제7권1호
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• pp.174-184
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• 1997

야자각탄으로부터 수증법을 이용하여 활성탄을 제조하였다. 활성화 온도와 시간, 수증기의 농도와 양이 n-butane 흡착특성에 미치는 영향을 비표면적, 기공분석, n-butane 흡착량을 측정함으로서 분석하였다. 90$0^{\circ}C$ 이하에서 활성화한 경우 온도와 시간이 증가하거나 수증기의 농도와 양이 많을수록 n-butane 흡착량은 증가하였으나 95$0^{\circ}C$에 이르면 이러한 경향은 나타나지 않았다. $900^{\circ}C$, 185분간 활성화한 시료는 비표면적 978 $\textrm{m}^2$/g, 평균기공 크기 9.3 $\AA$, n-butane 흡착랑이 5.9 g/100 ml이었다.

• 동력기계공학회지
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• 제9권4호
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• pp.96-101
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• 2005

Magnesium alloys have been widely used for many structural components of automobiles and aircraft because of high specific strength and good cast ability in spite of hexagonal closed-packed crystal structure of pure magnesium. In this study, uniaxial tension tests at high temperature and creep tests are done in order to investigate the characteristics of high temperature and mechanisms for creep deformation of AZ31 Mg alloy. Yield stress and ultimate tensile stress decreased with increasing temperature, but elongation increased from results of uniaxial tension test at high temperature. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined during creep of AZ31 Mg alloy over the temperature range of 473K to 573K and stress range of 23.42 MPa to 93.59 MPa, respectively, in order to investigate the creep behavior. Constant load creep tests were carried out in the equipment including automatic temperature controller, whose data are sent to computer. At around the temperature of $473K{\sim}493K$ and under the stress level of $62.43{\sim}93.59%MPa$, and again at around the temperature of $553K{\sim}573K$ and under the stress level of $23.42{\sim}39.00MPa$, the creep behavior obeyed a simple power-law relating steady state creep rate to applied stress and the activation energy for the creep deformation was nearly equal, respectively, and a little low to that of the self diffusion of Mg alloy including aluminum. Also rupture surfaces at high temperature have had bigger dimples than those at lower temperature by SEM.

• 한국진공학회지
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• 제8권4A호
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• pp.450-455
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• 1999

We present Photoluminescence (PL) and Atomic Force Microscopy (AFM) image on InAs quantum dots (QDs) having different size which grown by Molecualr Beam Epitaxy (MBE). For different size QDs, analysis of the AFM profiles show that the density of QDs was the maximum value $(1.1\times10^{11}\textrm{/cm}^2)$ at 2.0 ML. In the spectra of QDs, it is found that the peak energy decreases with increasing dot size due to the effect of quantum confinement. Temperature dependence of PL intensities show that the PL is quenching and Red shift as the temperature increase. The FWHM range of 20K~180K is narrowing with increasing temperature. When temperature is over 180K, the line-width starts to in creases with increasing temperature. At last, temperature dependence of the integrated intensities were fit using the Arrehenius-type function for the activation energy. Fit value of the activation energy was increased with increasing QDs-size.

• Carbon letters
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• 제15권2호
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• pp.146-150
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• 2014

In this work, activated carbon nanofiber (ACNF) electrodes with high double-layer capacitance and good rate capability were prepared from polyacrylonitrile nanofibers by optimizing the carbonization temperature prior to $H_2O$ activation. The morphology of the ACNFs was observed by scanning electron microscopy. The elemental composition was determined by analysis of X-ray photoelectron spectroscopy. $N_2$-adsorption-isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. ACNFs processed at different carbonization temperatures were applied as electrodes for electrical double-layer capacitors. The experimental results showed that the surface morphology of the CNFs was not significantly changed after the carbonization process, although their diameters gradually decreased with increasing carbonization temperature. It was found that the carbon content in the CNFs could easily be tailored by controlling the carbonization temperature. The specific capacitance of the prepared ACNFs was enhanced by increasing the carbonization temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.828-830
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• 1988

This paper considered temperature-sensitive characteristics on the basis of curie tempeature and quenching method in the process of manufacturing Mn-Cu-Zn Fersite. The results are as follow. Curie tempeature drops according as the content of CuO and ZnO increases. It also decreases according as sintering temperature increases when the content of ZnO in fixed. Curie temperature drops more in quenching than in slow cooling and activation energy diminishes were too. On the basis of curie tempeature, activation energy is greater in paramagnetic region than in ferrimagnetic region. As its voltage-crrent characteristics is similar to that semiconductors, the temperature-sensitive ferrite is expeated to be appied in the area of power electronics.

• Journal of Ginseng Research
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• 제9권2호
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• pp.248-255
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• 1985

In order to investigate the optimal drying condition of white ginseng by using bulk air drier(130 x 62 x 65cm), drying curves, diffusion coefficient at various drying temperature, the energy of activation, variation of color intensity and chemical components during drying of white ginseng were studied. Fick's second low of diffusion for diffusion out of spheres was successfully applied to describe the drying of white ginseng. It was found that the diffusion coefficient of water was 2.2x107, 9.0x107 cm2/sec at drying temperature 4$0^{\circ}C$, 55$^{\circ}C$, respectively. An Arrhenius type temperature dependency of moisture diffusivity was found, the energy of activation being 18.8 Kcal/g mol. Color intensity of white ginseng dried at various drying temperature was increased with an increase in drying temperature. The contents of crude protein, reducing sugar and crude saponin during drying of white ginseng were gradually decreased as increasing of drying time. And with the sensory evaluation by multiple comparison difference analysis, the optimal drying temperature of white ginseng was between 45$^{\circ}C$ and 5$0^{\circ}C$.

• 대한환경공학회지
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• 제29권5호
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• pp.515-520
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• 2007

현재 슬러지의 처리는 주로 해양투기에 의해 진행되는데 런던협약에 의해 슬러지 내 중금속 함량에 따라 점진적으로 해양투기가 완전 금지되어진다. 이에 하수슬러지의 안정적 처리 방안이 시급히 검토되어야 한다. 그 대책으로 최근 슬러지의 능률적이고 친환경적인 처리를 위한 방법 중 하나로 활성화를 통한 흡착제 제조가 부각되고 있다. 본 연구는 하수슬러지를 수증기 활성화법을 이용하여 흡착제로 활용하기 위한 기초연구로서 양질의 흡착제를 제조하기 위한 변수별 연구를 통한 최적 활성화조건을 연구하였다. 그 결과 요오드 흡착능을 기준으로 하여 변수별 연구를 통해 수증기 주입량 30 mL/hr, 활성화 온도 $500^{\circ}C$, 활성화 시간 60분으로 선정되었다. 이 때 요오드 흡착능과 수율은 228.4 mg/g, 77.23%로 나타났다. 또한 질소 흡착, SEM, EDS를 이용하여 수증기 활성화에 따른 세공 발달, 비표면적, 평균 세공경 및 화학적 성상과 함량을 파악하였다. 수증기 활성화를 통해 발달되는 세공은 주로 미세 세공임을 확인하였다.

• 한국환경과학회지
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• 제22권3호
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• pp.331-339
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• 2013

Efforts were made to determine the activation energy and the reaction order by adopting Kissinger and Flynn-Wall-Ozawa analysis methods. All the data were acquired from TGA thermograms for the mixed fuels with different temperature heating rates. It could be known that both the coal and the mixed fuels decomposed thermally at temperature ranges of $300{\sim}700^{\circ}C$. The temperature at the maximum reaction rate, Tp, could be determined by DTG method, which could be obtained by differentiation of TGA thermogram. Kissinger analysis showed the linear relationship with experimental data, showing the activation energy of $319.64{\pm}4$ kJ/mol. From Flynn-Wall-Ozawa analysis, it was shown that the activation energies and the reaction orders did not undergo any significant changes with both the conversions and the heating rates. It was considered from this facts that the combustion mechanism of the mixed fuels could not be affected by the extent of conversion and heating rate. In the present study, the activation energies showed different values according to the different analysis methods. The difference might be originated from the inconsistency of the mathematical data treatment method. In other words, while the activation energies obtained from the Kissinger method indicated the average values for overall reaction, that from Flynn-Wall-Ozawa method showed the average values for the each conversion around Tp.