• 공업화학
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• 제34권5호
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• pp.548-555
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• 2023

SAPO-34 catalysts were modified with polyethylene glycol (PEG) and Pb to improve their catalytic lifetime and selectivity for light olefins in the conversion of dimethyl ether to olefins (DTO). Hierarchical SAPO-34 catalysts and PbAPSO-34 catalysts were synthesized according to changes in the molecular weight of PEG (M.W. = 1000, 2000, 4000) and the molar ratio of Pb/Al (Pb/Al = 0.0015, 0.0025, 0.0035), respectively. By introducing PEG into the SAPO-34 catalyst crystals, an enhanced volume of mesopores and reduced acidity were observed, resulting in improved catalytic performance. Pb was successfully substituted into the SAPO-34 catalyst frameworks, and an increased BET surface area and concentration of acid sites in the PbAPSO-34 catalysts were observed. In particular, the concentrations of the weak acid sites, which induce a mild reaction, were increased compared with the concentrations of strong acid sites. Then, the P2000-Pb(25)APSO-34 catalyst was prepared by simultaneously utilizing the synthesis conditions for the P2000 SAPO-34 and Pb(25)APSO-34 catalysts. The P2000-Pb(25)APSO-34 catalyst showed the best catalytic lifetime (183 min based on DME conversion > 90%), with an approximately 62% improvement compared to that of the unmodified catalyst (113 min).

• 한국콘텐츠학회논문지
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• 제13권6호
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• pp.339-349
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• 2013

뇌손상 환자들을 대상으로 한국판 간이정신상태검사(MMSE-K)와 한국형 컴퓨터 신경행동검사(KCNT)를 실시하여 관련성을 평가하고, 확정적 정상군과 치매 의심군을 구분하는데 있어서 KCNT의 유용성을 평가하기 위하여 수행되었다. 뇌손상 환자 50명 중 확정적 정상군과 치매 의심군의 KCNT 결과는 정규성 검정을 만족하여 두 군간 비교는 t 검정을, MMSE-K와 KCNT 결과간에는 이변량 상관분석을 실시하였다. 두 군의 특성은 유의한 차이가 없었으며, KCNT 결과는 두 군간 모든 항목에서 유의한 차이가 있었다(p<.05). 두 검사간 Pearson 상관계수는 단순반응시간(r=-.580), 선택반응시간(r=-.341), 글자색 맞추기(r=-.661), 숫자구분(r=-.703), 두 자리 숫자더하기(r=-.582), 세 자리 숫자더하기(r=-.610), 부호숫자 짝짓기(r=-.642), 숫자외우기(r=.807)로 유의한 상관관계가 있었다(p<.05). 이 중 단순반응시간, 두 자리 숫자더하기는 확정적 정상군과 치매 의심군에서 서로 다른 부호의 상관계수를 나타내 두 군을 구분하는 검사로 사용할 수 있을 것으로 생각되며, 제안된 KCNT 항목들을 검사 목적에 따라 선택하여 사용하면 두 군의 인지기능을 관찰하기 위한 검사로 유용하게 사용할 수 있을 것으로 생각된다.

• 공업화학
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• 제30권1호
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• pp.81-87
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• 2019

에너지화 열가소성 탄성체 제조에 사용될 수 있는 새로운 계열의 glycidyl azide polymer (GAP)을 모색하기 위해 전구체인 poly(epichlorohydrin) (PECH)에 친핵체인 아지드기와 알콕시 및 알킬 아민을 도입하여 4가지 GAP copolymer polyol을 합성하고 물성에 대하여 고찰하였다. 이 GAP copolymer 합성반응은 이종의 친핵체를 1단계 반응으로 동시에 치환하여 미반응 sodium azide가 남지 않는 친환경적이며 효율적인 합성법으로 평가할 수 있다. 역개폐 짝풀림(inverse gated decoupling) $^{13}C$ NMR 분석법과 Fourier transform infrared (FT-IR) 분석법으로 상대적 치환율을 정량적으로 분석하였으며 반응 진행도를 모니터링 하였다. 합성된 GAP copolymer의 유리전이온도와 분자량은 differential scanning calorimetry (DSC)와 gel permeation chromatography (GPC)로 분석하였다. 합성된 poly($GA_{0.8}-butoxide_{0.2}$), poly($GA_{0.7}-n-butylamine_{0.3}$), poly($GA_{0.7}-dipropylamine_{0.3}$), poly($GA_{0.7}-morpholine_{0.3}$)의 유리전이온도는 $-39^{\circ}C$에서 $-26^{\circ}C$ 범위의 값을 나타내었다.

• 대한화학회지
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• 제67권3호
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• pp.191-198
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• 2023

본 연구에서는 2,4-dinitrophenyl-5-substituted-2-furoates (1a-d)와 R₂NH/R₂NH₂⁺-20 mol%DMSO(aq)의 아실 이동 반응을 반응속도론적으로 연구하였다. 이 반응은 이차반응이고, pK_a⁰ = 9.5, β₁= 0.23-0.35 및 β₂ = 0.88-0.99의 결과와 함께 아래 방향으로 굽은 Brönsted plots이 관측되었다. k₁값은 5-furyl 치환기의 전자끄는 능력이 증가하고 친핵체의 친핵성도가 커질수록 증가하였다. 반면, k₂/k_-1 값 비율은 5-furyl 치환기에 관계없이 거의 일정하였다. 실험결과로 부터 반응은 속도결정단계가 변하는 단계반응 메커니즘으로 진행됨을 제안하였다.

• 한국건설순환자원학회논문집
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• 제11권1호
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• pp.89-96
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• 2023

산업부산물인 페로실리콘을 사용한 시멘트 콘크리트의 내구성능을 평가하기 위하여 페로실리콘의 치환율을 3단계로 변화시켜 제조한 시멘트 경화체의 염화물침투저항성, 알칼리실리카 반응성에 대하여 평가하였다. 페로실리콘을 사용한 시멘트 콘크리트의 내구성능은 화학조성이 유사한 실리카흄과 비교하여 평가하였으며, 에너지 분산형 X선 분광법, 공극측정 및 X선 회절분석 등 기기분석을 통하여 페로실리콘 콘크리트의 미세 구조적 특성을 고찰하였다. 그 결과, 페로실리콘을 10 % 치환한 경우 OPC콘크리트보다 높은 강도발현 특성을 보인 반면 치환율이 20 %, 30 % 증가할수록 압축강도는 낮게 발현되었다. 그러나 염화물 침투저항성에 대한 결과는 치환율이 증가할수록 우수한 결과를 나타내었으며, 실리카흄을 사용한 경우에 비하여 페로실리콘을 사용한 콘크리트의 내구성은 약간 떨어지지만 OPC에 비해서는 우수한 결과를 나타내었다. 이는 페로실리콘의 실리카(SiO₂) 함량이 높아 더 많은 C-S-H 겔을 생성하여 더 밀실한 공극 구조를 만들었기 때문이라 생각된다. 길이변화시험을 통한 규산염 바인더에 대한 알칼리실리카반응의 위험성은 대부분 0.2 % 미만으로 나타났으며, 페로실리콘 및 실리카흄을 사용한 모르타르 모두 치환율이 증가할수록 알칼리실리카 반응에 대한 저항성은 우수한 것으로 나타났다. 따라서 고가의 실리카흄을 사용하는 대신 산업 폐기물을 재사용하면 제조 중 환경 부하를 줄이고 비용을 절약할 수 있을 것으로 판단된다.

• 한국재료학회지
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• 제22권2호
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• pp.103-109
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• 2012

Red-emitting $Eu^{3+}$-activated $(Y_{0.95-x}Al_x)VO_4$ (0 < x $\leq$ 0.12) nanophosphors with the particle size of ~30 nm and the high crystallinity have been successfully synthesized by a hydrothermal reaction. In the synthetic process, deionized water as a solvent and ethylene glycol as a capping agent were used. The crystalline phase, particle morphology, and the photoluminescence properties of the excitation spectrum, emission intensity, color coordinates and decay time, of the prepared $(Y_{0.95-x}Al_x)VO_4:Eu^{3+}$ nanophosphors were compared with those of the $YVO_4:Eu^{3+}$. Under 147 nm excitation, $(Y_{0.95-x}Al_x)VO_4$ nanophosphors showed strong red luminescence due to the $^5D_0-^7F_2$ transition of $Eu^{3+}$ at 619 nm. The luminescence intensity of $YVO_4:Eu^{3+}$ enhanced with partial substitution of $Al^{3+}$ for $Y^{3+}$ and the maximum emission intensity was accomplished at the $Al^{3+}$ content of 10 mol%. By the addition of $Al^{3+}$, decay time of the $(Y,Al)VO_4:Eu^{3+}$ nanophosphor was decreased in comparison with that of the $YVO_4:Eu^{3+}$ nanophosphor. Also, the substitution of $Al^{3+}$ for $Y^{3+}$ invited the improvement of color coordinates due to the increase of R/O ratio in emission intensity. For the formation of transparent layer, the red nanophosphors were fabricated to the paste with ethyl celluloses, anhydrous terpineol, ethanol and deionized water. By screen printing method, a transparent red phosphor layer was formed onto a glass substrate from the paste. The transparent red phosphor layer exhibited the red emission at 619 nm under 147 nm excitation and the transmittance of ~80% at 600 nm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• 한국자기학회지
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• 제20권5호
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• pp.182-186
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• 2010

Cobalt가 치환된 NiZnCu ferrite의 소결 및 자기적 성질에 미치는 영향에 대해 연구 하였다. 칩인덕터용 $Ni_{0.36-x}Co_xZn_{0.44}Cu_{0.22}Fe_{1.98}O_4(0{\leq}x{\leq}0.04)$를 고상반응법으로 제조하였다. 소결조제를 사용하지 않고 $880{\sim}920^{\circ}C$에서 공기중 2시간 열처리 하였으며 초투자율, 품질계수 Q, 밀도, 수축율, 포화자화, 및 보자력을 측정하였다. Cobalt가 치환된 NiZnCu ferrite는 품질계수 Q를 증가시켰으며 칩인덕터용으로 사용 가능함을 알 수 있었다. 품질계수 Q는 치환량이 x = 0.01까지 증가한 후 x = 0.01 이후로 급격히 감소하였다. Cobalt의 치환량이 증가함에 따라 초투자율 및 밀도값은 감소하였다. $900^{\circ}C$에서 소성된 $Ni_{0.35}Co_{0.01}Zn_{0.44}Cu_{0.22}Fe_{1.98}O_4$ 토로이달 core 샘플의 경우 1 MHz에서 측정 시 초투자율값은 130이었고 품질계수 Q값은 230으로 나타났다.

• 한국응용과학기술학회지
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• 제31권4호
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• pp.642-652
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• 2014

The synthesis of octenyl succinyl ${\beta}$-gucan (OSA-${\beta}$-glucan) was carried out and its interfacial properties at the oil-water interface and in emulsion systems were investigated. An aqueous ethanol system as a reaction media was used to facilitate the synthesis process; 10% (w/w) ethanol found to be the best as it showed a maximum degree of substitution (DS: 0.0132). FT-IR showed a characteristic absorption spectrum at $1736cm^{-1}$, indicating the esterification of octenyl succinyl groups to ${\beta}$-glucan backbone. As for interfacial tension measurements, it was decreased with increasing concentration of OSA-${\beta}$-glucan in the aqueous phase and when NaCl was added to aqueous OSA-${\beta}$-glucan solution in the range of 0.01 M to 0.1 M and also when pH was raised (pH 3 ~ pH 9). In systems of emulsion stabilized with OSA-${\beta}$-glucan, fat globule size found to decrease with increasing concentration of OSA-${\beta}$-glucan, showing a critical value of about $0.32{\mu}m$ at 0.5 wt%. When the OSA-${\beta}$-glucan emulsions were stored, it was found that fat globule size was increased with storage time and particularly pronounced increase was observed in emulsion with 1% OSA-${\beta}$-glucan, possibly due to depletion flocculation. Results of creaming stability evaluated by light scattering technique showed that it was more stable in emulsions containing smaller fat globule size. Surface load of OSA-${\beta}$-glucan in emulsions increased with increasing concentration of OSA-${\beta}$-glucan, suggesting a multilayer adsorption.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.250-250
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• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.