• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1153-1158
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• 1997

The powder characteristics of LiMn2O4 prepared by the citrate sol-gel method have been investigated. The optimum pH for the preparation of homogeneous citrate gel was calculated by the theoretical consideration of thermodynamic equilibrium constants for metal-citrate complexes and metal salts. The obtained citrate gel was prefired at 300 ℃ and calcined at 300-700 ℃ for 1 h. The obtained powders were characterized by TG/DSC, FT-IR spectrometer, X-ray diffractometer, SQUID magnetometer, SEM, and particle size analyzer. It was observed that the mixed phases of spinel LiMn2O4 and Mn3O4 were transformed into spinel LiMn2O4 phase and the vibrational bands due to the carbonate and nitrate were also disappeared over 400 ℃. At temperatures below 150 K, inverse molar susceptibilities of every sample began to show an antiferromagnetic ordering of Mn magnetic moments.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
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• pp.107-107
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• 1994

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.217-223
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• 1999

Proten-conductive $SrZr_{0.95} Y_{0.05} O_{2.975}$ powder was prepared by citrate gel method its characteristics and sinterability were investigated. Amorphous gel could be obtained from a citric acid solution that $SrCO_3$ and metal nitrates were dissolved. The initial decomposition of the gel proceeded up to $250^{\circ}C$, followed by combustion of its decomposition products in the temperature range from $250^{\circ}C$ to $500^{\circ}C$. A well-crystallized perovskite phase with a stoichiometric composition after calcination at $1000^{\circ}C$. Sintering green compacts of this powder for 6 h showed a considerable densification to start at $1200^{\circ}C$ and resulted in 86.8% and 96.5% relative densities at $1400^{\circ}C$ and $1600^{\circ}C$, respectively. Whereas, the powder compacts prepared by solid state reaction had much lower relative densities, 73% at $1400^{\circ}C$ and 92% at $1600^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1310-1314
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• 2011

Sodium beta-alumina (SBA) nano-powders were synthesized by the citrate sol-gel process, and the effects of the cationic surfactant n-cetyltrimethylammonium bromide surfactant (CTAB) were investigated. The structure and morphology of the nano-powders were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques, respectively. The effects of CTAB on the citrate sol-gel process and the SBA formation were investigated by thermo gravimetric/differential thermal analysis (TG/DTA) and Fourier transform infrared spectroscopy (FTIR). The conductivity of ceramic pellets of SBA was measured by electrochemical impedance spectroscopy (EIS). The results showed that the CTAB inhibited the agglomeration of SBA powders effectively and consequently decreased the crystallization temperature of SBA, about $150^{\circ}C$ lower than that of the sample without CTAB. The measured conductivity of SBA was $1.21{\times}10^{-2}S{\cdot}cm^{-1}$ at $300^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제36권1호
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• pp.93-97
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• 2023

A triboelectric nanogenerator (TENG) is a device that converts mechanical energy into electrical energy, and has been considered as a substitute for continuous power supply due to its high performance, simple structure and eco-friendliness. Recently, it is important to develop a TENG using a non-toxic material in order to use it as a power source for wearable, attachable, and body-embeddable electronics. Here, we developed a human friendly TENG using polyvinyl chloride (PVC) gel containing acetyl tributyl citrate (ATBC), a non-toxic plasticizer. PVC gels were fabricated using various ratios of PVC and ATBC, and optimized by investigating dielectric properties, surface potential, output performance, and durability. The PVC gel based TENG generates output signals of 73 V and 4.3 μA, i.e., a 5-fold enhancement in the output power compared to pristine PVC-based TENG. In addition, the PVC gel can be stretched over 500% of strain. This study is expected to be helpful in the future development of non-toxic wearable TENG.

• BMB Reports
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• 제42권12호
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• pp.812-816
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• 2009

To screen chaperone proteins from Schizosaccharomyce pombe (S. pombe), we prepared recombinant citrate synthase of the fission yeast as a substrate of anti-aggregation assay. Purified recombinant citrate synthase showed citrate synthase activity and was suitable for the substrate of chaperone assay. Several heat stable proteins including aspartyl aminopeptidase (AAP) for candidates of chaperone were screened from the supernatant fraction of heat-treated crude extract of S. pombe. The purified AAP migrated as a single band of 47 kDa on SDS-polyacrylamide gel electrophoresis. The native size of AAP was estimated as 200 kDa by a HPLC gel permeation chromatography. This enzyme can remove the aspartyl residue at N-terminus of angiotensin I. In addition, AAP showed the heat stability and protected the aggregation of citrate synthase caused by thermal denaturation. This study showed that S. pombe AAP is a moonlight protein that has aspartyl aminopeptidase and chaperone activities.

• 대한화학회지
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• 제38권4호
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• pp.276-282
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• 1994

Citrate sol-gel법을 이용하여 perovskite형 복합산화물 LaBO$_3$(B = Mn, Fe, Co)을 공기 중 $850^{\circ}C$에서 24시간 동안 소성하여 제조하였다. X-선 회절분석(XRD)과 TPR결과에 의하면 이들 산화물의 결정구조와 산소화학양론은 LaMnO$_{3.16}$(a = 5.507, c = 13.329 $\AA$, hexagonal), LaFeO$_{3.17}$(a = 5.554, b = 5.555, c = 7.863 $\AA$, orthorhomibic), LaCoO$_{3.0}$(a = 5.436, c = 13.095 $\AA$, hexagonal)으로 수소 분위기(300torr)에서의 TPR결과에 의하면 이들 산화물은 2단계 환원반응으로 반응이 진행되며, 열적안정성은 LaMnO$_3$ > LaFeO$_3$ > LaCoO$_3$순으로 나타났고, 반응속도론적 결과 역시 LaCoO$_3$의 활성화에너지 값이 가장 낮음을 보였다.

• 대한핵의학회지
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• 제22권1호
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• pp.77-81
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• 1988

Tumor localizing properties of $^{67}Ga$ citrate and $^{169}Yb$ citrate were studies with sarcoma 180 bearing mice. To compare precisely the accumulation of $^{67}Ga$ citrate and $^{169}Yb$ citrate in tumor tissue itself, $^{67}Ga$ and l63yb were administered simultaneously as a mixture of same chemical form of citrate. The yield of $^{169}Yb$ labeled citrated and the of radiopharmaceuticals purity was identified more than 90% by chromatography on silica gel plates. $^{67}Ga$ and $^{169}Yb$ were injected into mice and the mice were killed at 3, 24, and 48 hours following intraperitoneal injection of the radiopharmaceuticals. The retention value of $^{67}Ga$ and $^{169}Yb$ in tumor was similar but they differ from each other markedly in normal tissue distribution. $^{169}Yb$ citrate is cleared up from blood more rapidly than $^{67}Ga$ citrate, and a high tumor to blood ratio is achieved shortly after injection.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.557-560
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• 2003

The submicron $YBa_2Cu_3O_x$ powder was prepared by the sol-gel method. The particle size is distributed from 0.2 to $1.0\;{\mu}m$, which benefits to eliminate the micro-cracks formed in the $YBa_2Cu_3O_x$ films deposited by electrophoresis. The powder was single phase of $YBa_2Cu_3O_x$ examined by X-ray diffraction. In the sol-gel process the citrate gel was formed from citric acid and nitrate solution of $Y_2O_3$, $Ba(NO_3)O_2$ and CuO. When pH values were adjusted to $6.4{\sim}6.7,\;Ba(NO_3)O_2$ could be dissolved in the citrate solution completely. Appropriate evaporative temperature of the sol-gel formation is discussed. After the heat treatment the transition temperature($T_c$) and critical current density($J_c$) of the $YBa_2Cu_3O_x$ samples made of the submicron powder were measured.

• 동굴
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• 제76호
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• pp.49-55
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• 2006

The submicron $YBa_2Cu_3O_x$ powder was prepared by the sol-gel method. The particle size is distributed from 0.2 to 1.0 ${\mu}m$, which benefits to eliminate the micro-cracks formed in the $YBa_2Cu_3O_x$ films deposited by electrophoresis. The powder was single phase of $YBa_2Cu_3O_x$ examined by X-ray diffraction. In the sol-gel process the citrate gel was formed from citric acid and nitrate solution of $Y_2O_3$, $Ba(NO_3)_2$ and CuO. When pH values were adjusted to 6.4-6.7, $Ba(NO_3)_2$ could be dissolved in the citrate solution completely. Appropriate evaporative temperature of the sol-gel formation is discussed. Acetone is used as electrophoreticsolution, in which some water and iodine (0.2 g/1) and polyethylene glycol (2 vol. %) are added. The concentrations of $YBa_2Cu_3O_x$ powders is 20g/l. The thickness of deposited film could be more than 50 ${\mu}m$ in 3 minutes of depositing time. The most EPD films could be 90K zero resistance and the Jc values were over 1000A/cm2 (0 H, 77 K).