• 한국환경과학회지
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• 제13권7호
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• pp.619-626
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• 2004

We have studied the catalytic combustion of soot particulates over perovskite-type oxides prepared by malic acid method, The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions such as temperature and $O_2$ concentration were investigated. The partial substitution of alkali metals into A site in the $LaMnO_3$ catalyst, enhanced the catalytic activity in the combustion of carbon particulate and the activity was shown in the order: Cs > K > Na. For the $La_{1-x}Cs_{x}MnO_{3}$ catalysts, the catalytic activity showed the maximum value with x=0.3 but no more increase on the catalytic activity was shown with x > 0.3. For the $La_{0.8}Cs_{0.2}MnO_{3}$ catalyst, the substitution of Fe or Ni increased the ignition temperature. The ignition temperature decreased with an increase of $O_2$ concentration, however, no more increase in the catalytic activity was shown with $O_2$ concentration > 0.2. The introduction of NO into reactants showed no effect on the catalytic activity.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.28.2-28.2
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• 2011

Resistance random access memory (ReRAM) is a promising candidate for next-generation nonvolatile memory because of its advantageous qualities such as simple structure, superior scalability, fast switching speed, low-power operation, and nondestructive readout. We investigated the resistive switching behavior of tantalum oxide that has been widely used in dynamic random access memories (DRAM) in the present semiconductor industry. As a result, it possesses full compatibility with the entrenched complementary metal-oxide-semiconductor processes. According to previous studies, TiN is a good oxygen reservoir. The TiN top electrode possesses the specific properties to control and modulate oxygen ion reproductively, which results in excellent resistive switching characteristics. This study presents fully room temperature fabricated the TiN/$TaO_x$/Pt devices and their electrical properties for nonvolatile memory application. In addition, we investigated the TiN electrode dependence of the electrical properties in $TaO_x$ memory devices. The devices exhibited a low operation voltage of 0.6 V as well as good endurance up to $10^5$ cycles. Moreover, the benefits of high devise yield multilevel storage possibility make them promising in the next generation nonvolatile memory applications.

• 한국재료학회지
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• 제14권6호
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• pp.420-424
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• 2004

The microstructure and electrical properties of $ZnO-Pr_{6}$$O_{11}$ $-CoO-Y_2$$O_3$-based varistors were investigated with and without various metal oxide additives (NiO, MgO, and $Cr_2$$O_3$). The addition of NiO promoted the grain growth while that of Cr$_2$O$_3$ decreased average grain size. Thereby, the varistor voltage was higher in $Cr_2$$O_3$-added composition. Among $ZnO-Pr_{6}$ $O_{11}$ /$-CoO-Y_2$$O_3$-based varistors, the$ Cr_2$$O_3$-added varistor exhibited the highest nonlinear exponent (51.2), the lowest leakage current (1.3 $\mu$A), and the lowest dielectric dissipation factor (0.0433).

• 대한화학회지
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• 제33권3호
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• pp.315-320
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• 1989

철광석 중에 존재하는 미량 금속원소들을 분석하는 방법을 제시하였다. 분석방법은 ammonium pyrrolidinedithiocarbamate(APDC)-methyl isobutyl ketone(MIBK) 추출계와 원자흡수 분광법(AA)를 이용하였다. 철이 유기층으로 추출되는 것을 막기 위하여 가리움제로서 코발트, 니켈 및 구리의 분석시에는 pH $8{\sim}10$에서 citrate를, 그리고 망간 및 구리의 분석시에는 pH 6{\sim}7$에서 tiron을 가하였다. MIBK의 물에 대한 용해도를 줄이기 위해 NaCl을 염석제로 가하였다. 금속 추출용액의 안정도를 증가시키기 위한 방안으로 MIBK 금속 추출물을 질산 수용액으로 역추출하는 것을 검토하였다.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1199-1203
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• 2012

Catalytic filters consisting of Ni nanoparticle and carbon fiber with different oxidation states of Ni (either metallic or oxidic) were prepared using a chemical vapor deposition process and various post-annealing steps. CO oxidation reactivity of each sample was evaluated using a batch type quartz reactor with a gas mixture of CO (500 mtorr) and $O_2$ (3 torr) at $300^{\circ}C$. Metallic and oxidic Ni showed almost the same CO oxidation reactivity. Moreover, the CO oxidation reactivity of metallic sample remained unchanged in the subsequently performed second reaction experiment. We suggested that metallic Ni transformed into oxidic state at the initial stage of the exposure to the reactant gas mixture, and Ni-oxide was catalytically active species. In addition, we found that CO oxidation reactivity of Ni-oxide surface was enhanced by increase in the $H_2O$ impurity in the reactor.

• 한국재료학회지
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• 제28권12호
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• pp.685-690
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• 2018

In this study, a multifunctional ophthalmic lens material with an electromagnetic shielding effect, high oxygen permeability, and high water content is tested, and its applicability is evaluated. Metal oxide nanoparticles are applied to the ophthalmic lens material for vision correction to shield harmful electromagnetic waves; the pyridine group is used to improve the antibacterial effect; and silicone substituted with urethane and acrylate is employed to increase the oxygen permeability and water content. In addition, multifunctional tinted ophthalmic lens materials are studied using lens materials with an excellent antibacterial effect (2,6-difluoropyridine, 2-fluoro-4-pyridinecarboxylic acid) and functional (UV protection, high wettability) lens materials (2,4-dihydroxy benzophenone, 2-hydroxy-4-(methacryloyloxy)benzophenone). To solve problems such as air bubbles generated during the polymerization process for the manufacturing and turbidity of the lens surface, polymerization conditions in which the defect rate is minimized are determined. The results show that the polymerization temperature and time are most appropriate when they are $110^{\circ}C$ and 40 minutes, respectively. The optimum injection amount of the polymerization solution is 350 ms. The turbid phenomenon that appears in lens processing is improved by 10 to 95 % according to the test time and conditions.

• Journal of Animal Science and Technology
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• 제63권5호
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• pp.1159-1168
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• 2021

Ovotransferrin (OTF), an egg protein known as transferrin family protein, possess strong antimicrobial and antioxidant activity. This is because OTF has two iron binding sites, so it has a strong metal chelating ability. The present study aimed to evaluate the improved immune-enhancing activities of OTF hydrolysates produced using bromelain, pancreatin, and papain. The effects of OTF hydrolysates on the production and secretion of pro-inflammatory mediators in RAW 264.7 macrophages were confirmed. The production of nitric oxide (NO) was evaluated using Griess reagent and the expression of inducible nitric oxide synthase (iNOS) were evaluated using quantitative real-time polymerase chain reaction (PCR). And the production of pro-inflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-6) and the phagocytic activity of macrophages were evaluated using an ELISA assay and neutral red uptake assay, respectively. All OTF hydrolysates enhanced NO production by increasing iNOS mRNA expression. Treating RAW 264.7 macrophages with OTF hydrolysates increased the production of pro-inflammatory cytokines and the phagocytic activity. The production of NO and pro-inflammatory cytokines induced by OTF hydrolysates was inhibited by the addition of specific mitogen-activated protein kinase (MAPK) inhibitors. In conclusion, results indicated that all OTF hydrolysates activated RAW 264.7 macrophages by activating MAPK signaling pathway.

• Corrosion Science and Technology
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• 제21권4호
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• pp.290-299
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• 2022

Anodizing is an electrochemical surface treatment method conferring corrosion resistance and durability by forming a thick anodization film on the metal surface. Aluminum has a long service life and high thermal conductivity and formability, as well as excellent corrosion resistance. Aluminum 3003 alloy has improved formability, strength, and corrosion resistance due to the addition of a small amount of manganese. However, corrosion occurs in seawater and environments polluted with corrosion-inducing substances, which reduce corrosion resistance. Therefore, it is necessary to artificially form a thick anodized film to improve corrosion resistance. In this study, the anodization treatment time was 4 minutes, and voltages of 10 V, 20 V, 30 V, 40 V, 50 V, 60 V, 70 V, 80 V, 90 V, and 100 V were applied. The thickness and pore size of the oxide film increased according to the applied voltage. A barrier film was formed under voltage conditions from 10 V to 50 V, and a porous film was formed under voltage conditions from 60 V to 100 V. After anodizing, coating was applied. Wettability and corrosion resistance were observed before and after coating according to the surface shape and thickness of the oxide film.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.709-715
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• 2001

We have been studied photosensitization mechanism's additive effect, of perylene 3,4,9,10-tetracarboxyl-diimide and X-phthalocyanine (charge generation materials), using the photochemical and photoelectrochemical approach. It was found that the photoreceptor on the excited state reacts with metal oxide, which creates the charge transfer on the interface of SnO2/electrolyte. In the electrode (X5P1) made of five X-phthalocyanine and single perylene 3,4,9,10-tetracarboxyldiimide layers, the cathodic photocurrent of X-phthalocyanine in the 400-600 nm region was increased by the addition of perylene 3,4,9,10-tetracarboxyldiimide. The maximum wavelength of fluorescence of perylene 3,4,9,10-tetracarboxyldiimide showed no dependence on the temperature. The addition of 4-dibenzylamino-2-methylbenzaldehyde diphenylhydrazone known as charge transport material was represented as decreasing photocurrent for X-phthalocyanine and perylene 3,4,9,10-tetracarboxyldiimide, respectively. In the electrode (X1P1) made of single X-phthalocyanine and single perylene 3,4,9,10-tetracarboxyldiimide layers, an anodic photocurrent of about 10.5 nA was generated by addition of hydroquinone at 550 nm. And the characteristic of photoinduced discharge was shown to decrease by a factor of 5 and the speed of dark decay was increased by a factor of 1.2.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.74-77
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• 2002

Ferroelectric Random Access Memory(FRAM) and MEMS applications require noble metal or refractory metal oxide electrodes. In this study, Ru thin films were etched using $O_2$+10% $CF_4$ plasma in an inductively coupled plasma(ICP) etching system. The etch rate of Ru thin films was examined as function of rf power, DC bias applied to the substrate. The enhanced etch rate can be obtained not only with increasing rf power and DC bias voltage, but also with small addition $CF_4$ gas. The selectivity of $SiO_2$ over Ru are 1.3. Radical densities of oxygen and fluorine in $CF_4/O_2$ plasma have been investigated by optical emission spectroscopy(OES). The etching profiles of Ru films with an photoresist pattern were measured by a field emission scanning electron microscope (FE-SEM). The additive gas increases the concentration of oxygen radicals, therefore increases the etch rate of the Ru thin films and enhances the etch slope. In $O_2$+10% $CF_4$ plasma, the etch rate of Ru thin films increases up to 10% $CF_4$ but decreases with increasing $CF_4$ mixing ratio.