• 세라미스트
• /
• 제10권3호
• /
• pp.67-74
• /
• 2007

Crystallisation kinetics of the erbium doped soda-tellurite glasses were studied using the differential thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques. The DTA curves in the temperature range of 350 K to 650 K were obtained from isochronal heating rates, chosen in the range of 2 to 20 K/min. DSC isothermal curves were used to calculate the fraction of crystals formed on reheating. The apparent activation energies for devitrification were derived by measuring the shifts in the values of $T_g$ and $T_x$ with heating rates, using the Kissinger method. The derived values of apparent activation energies for isochronal and isothermal methods varied in the range of $190-204\;{\pm}\;5\;kJ\;mol^{-1}$. The X-ray powder diffraction analysis of heat treated and transparent samples showed the presence of nano-scale size sodium-tellurite crystals. These crystallites were found to have a strong influence on the full width of half maxima of the transition in $Er^{3+}:\;^4I_{13/2}{\rightarrow}^4I_{15/2}$, which extended from 70 nm in the vitreous materials to 132 nm in glass-ceramic materials.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2009년도 추계학술발표대회
• /
• pp.48.2-48.2
• /
• 2009

구리 나노분말은 우수한 전기전도도와 상대적으로 저렴한 가격으로 주목을 받고 있어이를 이용한 다양한 기술들이 개발 중에 있다. 이들 중 잉크젯 프린팅용 구리 나노잉크는 기존의 포토리소그래피방식의 복잡한 공정단계와 이로 인한 단가 인상을 해결할 수 있는 공정으로 기대되는 잉크젯 프린팅에 구리를 사용할 수 있게 해주어 광범위한 응용이가능할 것으로 기대되어 많은 연구가 진행되고 있는 분야이다. 실제로 구리 나노분말의 이용하게 될 때에있어서 어려운 점 중 하나가 바로 빠른 표면 산화의 문제이다. 이를 막기 위해 본 연구에서는 건식 분말코팅 방법을 이용해 octanethiol 자기조립박막을 구리 표면에 부착한 분말을 사용하여 구리 나노분말용액을 제조하는 실험을 수행하였다. 건식 분말 코팅에 의해 산화 방지막이 부착된 분말을 표면 활성제인 Diethanolamine을 이용해 안정적으로 분산시켜 잉크로 사용이 가능한 용액을 제조해 보고, 분산된 용액의 안정도를 확인하기 위해 zetapotential analyzer를이용하여 분산도를 분석하였다. 또한 분산된 용액의 활용 실험을 위해 유리 기판에 바른 용액을 질소 분위기의튜브로에서 $250^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$의 온도에서 30분간 소결을 진행한 후 probe-station을 이용하여 전기 전도도를 측정하였다. 이렇게제작된 샘플은 Scanning Electronic Microscope 를 이용하여 소결된 상태의 표면의 사진을 찍어 서로 비교해보았다. $300^{\circ}C$에서 소결한 시편부터 소결이 시작되어 $400^{\circ}C$에서 소결한 시편은 다량의 소결목이 형성되었다.

• 한국수소및신에너지학회논문집
• /
• 제10권1호
• /
• pp.49-57
• /
• 1999

In order to study the effect of high energy ball milling on the $Mg_2Ni+Ni$, $Mg_2Ni+0.5Ni+0.5Al$ powders, we have investigated on the discharge properties, microstructures. The powder size of samples decreased as ball milling time. From the XRD results, the crystal structure of $Mg_2Ni+Ni$ mixed powders were changed to amorphous or nano-structure after 60hr ball milling. The discharge capacities of both $Mg_2Ni+Ni$ and $Mg_2Ni+0.5Ni+0.5Al$ powders increased, with increasing ballmilling time, the maximum capacity(342mAh/g) was shown for the 60 hrs ballmilled $Mg_2Ni+Ni$ sample. The capacity decreased drastically after a few charge-discharge cycles.

• 한국전기전자재료학회논문지
• /
• 제25권3호
• /
• pp.224-228
• /
• 2012

We have developed new materials that lead to methyl meth acrylate monomer and styrene monomer to using polymerization method. The materials have a powder form and show liquid behavior. We call the "Electronic Bead". An our experiment, a positive-charged particle has $TiO_2$, polymer and CCA(-), while a negative-charged particle consists of carbon black, polymer and CCA(+). The charged particles have electrical characteristic of white -10 uC/g and black 10 uC/g, respectively. Also, these particles have good fluidity by additive of nano-sized silica. Using these materials, we demonstrated prototype displays that have $320{\times}320$ array of pixels and 6-in-diagonal viewable image size, driven by passive-matrix addressing. The reflectivity shows about 30% even though our experiment is at the beginning point. Also, the panel has contrast ratio 6:1. We think there are many chances to improve reflectivity through modifying components of particle resin, mixture ratio of each particle, panel structure and so on.

• Journal of Electrical Engineering and Technology
• /
• 제3권1호
• /
• pp.115-120
• /
• 2008

Use of the carbon nanotube is superior to general powder state materials of mechanical and electrical properties. Because its ratio of diameter and length (aspect ratio) is very large, it has been known as a type of ideal nano-reinforcement material. Based on this advantage, the existing carbon black of semiconductive shield materials used in power cables can acquire excellent properties by using a small amount of carbon nanotubes. Thus, we investigated the thermal properties of the carbon nanotube, such as thermal conductivity, specific heat, and DSC (Differential Scanning Calorimetry). We found that a high thermal resistance level is demonstrated by using a small amount of carbon nanotubes. As a result, this tendency confirms high cross-linking density in a new network in which the carbon nanotube between carbon black constitute molecules shows a bond by similar constructive properties.

• Advances in nano research
• /
• 제5권3호
• /
• pp.203-214
• /
• 2017

In this study we present the reaction mechanism of $Cu_2ZnSnSe_4$ (CZTSe) nanoparticles synthesized by microwave-assisted chemical synthesis. We performed reactions every 10 minutes in order to identify different phases during quaternary CZTSe formation. The powder samples were analyzed by x-ray diffraction (XRD), Raman spectroscopy, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that in the first minutes copper phases are predominant, then copper and tin secondary phases react to form ternary phase. The quaternary phase is formed at 50 minutes while ternary and secondary phases are consumed. At 60 minutes pure quaternary CZTSe phase is present. After 60 minutes the quaternary phase decomposes in the previous ternary and secondary phases, which indicates that 60 minutes is ideal reaction time. The EDS analysis of pure quaternary nanocrystals (CZTSe) showed stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. In conclusion, the evolution pathway of CZTSe synthesized by this novel method is similar to other synthesis methods reported before. Nanoparticles synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

• Journal of Microbiology and Biotechnology
• /
• 제21권8호
• /
• pp.869-873
• /
• 2011

Most medium formulations for improving culture of entomopathogenic nematodes (EPN) based on protein sources have used enriched media like animal feed such as dried egg yolk, lactalbumin, and liver extract, among other ingredients. Most results, however, showed unstable yields and longer production time. Many of the results do not show the detailed parameters of fermentation. Soy flour, cotton seed flour, corn gluten meal, casein powder, soytone, peptone, casein hydrolysates, and lactalbumin hydrolysate as protein sources were tested to determine the source to support optimal symbiotic bacteria and nematode growth. The protein hydrolysates selected did not improve bacterial cell mass compared with the yeast extract control, but soy flour was the best, showing 75.1% recovery and producing more bacterial cell number ($1.4{\times}10^9$/ml) than all other sources. The highest yield ($1.85{\times}10^5$ IJs/ml), yield coefficient ($1.67{\times}10^6$ IJs/g medium), and productivity ($1.32{\times}10^7$ IJs/l/day) were also achieved at enriched medium with soybean protein.

• Preventive Nutrition and Food Science
• /
• 제22권1호
• /
• pp.50-55
• /
• 2017

Raphanus sativus L. (RS) is a cruciferous vegetable that is widely consumed in Korea. The anticancer activity of leaves of RS (RSL) extract has been investigated; however, no studies focused on its anti-inflammatory effects. Therefore, the aim of the current study was to evaluate the anti-inflammatory effects of RSL extract. In brief, RSL powder was fractionated into n-hexane, chloroform, ethyl acetate, n-butanol, and water-soluble fractions. Lipopolysaccharide (LPS)-stimulated RAW264.7 cells were treated with each fraction for initial screening. It was found that the chloroform fraction significantly inhibited nitric oxide release in LPS-stimulated RAW264.7 cells with a half maximal inhibitory concentration value of $196{\mu}g/mL$. In addition, the mRNA and protein expression levels of inducible nitric oxide synthase, measured using reverse transcriptase-polymerase chain reaction and western blotting, respectively, were reduced in a concentration-dependent manner. Moreover, the inflammatory cyclooxygenase-2 enzyme expression decreased. Furthermore, the expression of nuclear factor-kappa B ($NF-{\kappa}B$), the key regulator of the transcriptional activation of the inflammatory cytokine genes, was reduced by the RSL chloroform fraction. Therefore, the results of our study suggest that RSL exhibits anti-inflammatory effects in LPS-stimulated macrophages via $NF-{\kappa}B$ inactivation.

• 한국세라믹학회지
• /
• 제45권2호
• /
• pp.99-104
• /
• 2008

Zeta potential, sedimentation bulk density and rheology in the dispersion system have been studied in terms of solid loading (40-55 vol%), and types of additives. Ammonium polymethacrylate, glycerol, ethoxylated acetylenic diol, and polyvinyl alcohol have been used as the dispersant, cryo-protectant, surfactant, and binder, respectively. Sedimentation density greatly increased upon adding dispersant; the effect was more pronounced with ionic alumina suspension compared with covalent silicon carbide. With further addition of cryo-protectant and surfactant to dispersant, the sedimentation density increased somewhat. The suspension viscosity generally behaviored in an opposite manner to the sedimentation density, i.e., high sedimentation gave low high-shear viscosity, indicative of low order structure formation in the suspended particles. Shear rate rheology in shear rate of $2-300\;sec^{-1}$ showed a shear thinning and its onset began at similar shear rate (${\sim}100\;sce^{-1}$), regardless of solid loading.

• Advances in nano research
• /
• 제3권1호
• /
• pp.1-11
• /
• 2015

Thin film ethanol sensors made from ${\alpha}-Fe_2O_3$ decorated with multiwall carbon nanotubes(MWCNTs) were manufactured by the electron beam deposition method. The morphology of the decorated ${\alpha}-Fe_2O_3$/MWCNTs (25:1 weight ratios) nanocomposite powder was investigated using the scanning electron microscopy and X-ray diffraction techniques. The thickness of thin films has been determined from ellipsometric measurements. The response of manufactured sensors was investigated at different temperatures of the sensor work body and concentration of gas vapors. Good response of prepared sensors to ethanol vapors already at work body temperature of $150^{\circ}C$ was shown.