• Clean Technology
• /
• v.18 no.4
• /
• pp.366-372
• /
• 2012

Three acrylic copolymers containing tris(8-hydroxyquinoline) aluminum (AlQ3) pendant group (25 wt%), acrylateco-HEMA-$AlQ_3$ (25 wt%), were successfully synthesized by free radical polymerization from acrylates [methyl methacrylate (MMA), acrylonitrile (AN) or 2-hydroxyethyl methacrylate (HEMA)] with HEMA functionalized with AlQ3 pendant groups (HEMA-p-$AlQ_3$). The glass transition temperatures ($T_g$) of MMA-co-HEMA-p-$AlQ_3$ (copolymer 1), AN-co-HEMA-p-$AlQ_3$ (copolymer 2) and HEMA-co-HEMA-p-$AlQ_3$ (copolymer 3) were found to be 158, 150 and $126^{\circ}C$, respectively. They have good thermal stability: a very desirable feature for the stability of OLEDs. Their solubility, thermal properties, UV-visible absorption and photoluminescence behaviors were investigated. They were found to be soluble in various organic solvents such as tetrahydrofuran (THF), dimethylformamide (DMF), toluene and chloroform. It was also found that the UV-visible absorption and photoluminescence behaviors of these copolymers were similar to those of pristine $AlQ_3$. Green organic light-emitting diodes (OLEDs) have also been fabricated using these copolymers as light emission/electron transport components obtained easily by spin coating, and their current density voltage (J-V) curves were compared. The OLED device of the copolymer 3 had the lowest turn-on voltage of about 2 V compared to other copolymer types devices.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.1
• /
• pp.6-17
• /
• 1997

Lithium niobate single crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varing between 48.6 ~ 58.0 mol % $Li_2O$. A vapor transport equilibration technique has been used to improve the homogeneity and adjust the [Li]/[Nb] ratio in small $LiNbO_3$ single crystals grown by the Czochralski method. When equilibrated with a Li-rich powder (65 mol%$Li_2O$), containing a mixture of $LiNbO_3$ and $Li_3NbO_4$, crystals of nearly stoichiometric composition can be obtained. This was established by studying the composition dependence of the following properties; lineshape, intensity and linewidth for the electron paramagnetic resonance (EPR) of $Fe^{3+}$ energy of the fundamental absorption edge and $OH^-$ absorption spectra.

• Korean Chemical Engineering Research
• /
• v.49 no.2
• /
• pp.175-180
• /
• 2011

In this study, the $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors were prepared by mixing $TiO_{2}$ and $V_{2}O_{5}$, and a subsequent smash process to reduce the recombination of electron and improve the efficiency of solar cells. Dye-sensitized solar cells were constructed using the resultant hybrid semiconductor, and their electrochemical properties were also investigated. The photocurrent-voltage curve obtained with the cells indicated a significant increase in the efficiency from 2.9 to 5.7% by the factor of 2 compared to the result obtained only with $TiO_{2}$. It is believed that the introduction of $V_{2}O_{5}$ effectively transport electrons in the $TiO_{2}$ conduction band to FTO glass and suppress recombination with the dye and/or the electrolyte, thus yielding an efficient performance of the dye sensitized solar cell. The impedance values also indicated a decrease of resistance in the interface of $TiO_{2}$/dye/electrolyte supporting the constructive contributions of the smashed $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors for the efficiency.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.260-269
• /
• 2002

The fire resistance of particulate polypropylene composite systems were investigated by using various reinforced particles such as zeolite, talc, $CaCO_3$ particles. In this study, The effect of particle size on the thermal properties of composite and the effect of reinforced particles on the fire resistance were studied. The inorganic reinforced particles used in this study were recycled zeolite(average particle diameter=85.34 $mu extrm{m}$), $CaCO_3$ (33.93 $mu extrm{m}$), and talc (18.51 $mu extrm{m}$). The fire resistance of composite systems was thoroughly examined by measuring limited oxygen index (LOI, ASTM D2863) and cone calorimetry (ASTM E1354, ISO 5660). Thermal stability of composite systems was thoroughly examined by measuring TGA. The flame retardants (DBDPO) and reinforced particles reduce the maximum heat release rate (M-HRR) in the order of Talc > $CaCO_3$ > recycled Zeolite. Comparing the cone calorimetry experimental results of the particle reinforced polymer composite system exhibited twice higher efficiency than DBDPO in polypropylene systems, and the LOI also showed similar trends to the cone calorimetry experiments. The optical and scanning electron microscopy techniques were used to investigate the composites ash layer and the core fracture surfaces in the burning process. The reinforcing inorganic particles seemed to accumulate at the surface of ash layer, and subsequently intercept the oxygen transport and heat transfer into the core area.

• Applied Microscopy
• /
• v.33 no.4
• /
• pp.261-266
• /
• 2003

The growth patterns of primary culture of bovine brain microvessel endothelial cells (BBMECs) were studied using electron microscopy when grown on $3.0{\mu}m$ and $0.4{\mu}m$ pore Transwell. The capillary fragments and isolated endothelial cells grew on collagen coated culture plate and Transwell membrane. The BBMECs grew only on the upper surface of membrane of $0.4{\mu}m$. But BBMECs on $3.0{\mu}m$ pore membrane migrated through the pore and grew on the opposite side of the membrane. In summary, BBMECs isolated by enzyme digestion could migrate through $3.0{\mu}m$ pore membrane but not through $0.4{\mu}m$ pore membrane. So $0.4{\mu}m$ pore membrane instead of $3{\mu}m$ pore membrane should be used for drug transport experiment or transendothelial electrical resistance measurement.

• Korean Journal of Veterinary Research
• /
• v.36 no.3
• /
• pp.551-563
• /
• 1996

This study investigated the properties of primary cultured proximal tubule cells in hormonally defined(insulin, transferrin, and hydrocortisone), serum-free medium or 10% serum-supplemented medium. The growth rate of the primary cultured proximal tubule cells was lower in the hormonally defined, serum-free medium than in the 10% serum- supplemented medium(p < 0.05), while the activities of brush border marker enzymes, alkaline phosphatase(AP), leucine aminopeptidase(LAP), and y-glutamyl transpeptidase(${\gamma}$-GTP) were increased(p < 0.05). The activities of these enzymes, however, decreased with the lapse of incubation time to 50-70% after 6 days culture compared to those of the freshly-prepared proximal tubules. The enzymatic activities of the primary cultured proximal tubul cells on 6, 9, 12, and 15 days of culture were significantly increased in the hormonally defined, serum-free medium compared to the 10% serum-supplemented medium(p < 0.05). The functional differentiation of the primary culture was examined by observing multicellular domes of the confluent monolayer, which is indicative of transepithelial solute transport. The dome formation by the proximal tubule cultures occurred at a higher frequency in the hormonally defined, serum-free medium than in the 10% serum-supplemented medium(p < 0.05). Upon electron microscopic examination, an increased density of the brush border was observed in the hormonally defined, serum-free medium compared to the cells grown in 10% serum-supplemented medium. The activities of $Na^+$glucose cotransporter($^{14}C$-a-MG uptake), $Na^+$phosphate cotransportere($^{32}P$ uptake) and $Na^+$ transporter($^{22}Na^+$ uptake) in the brush border membrane, and of $Na^+/K^+$-ATPase($^{86}Rb$ uptake) in the basolateral membrane were significantly stimulated in the hormonally defined, serum-free medium than in 10% serum-supplemented medium(p < 0.05). In conclusion, the primary cultured proximal tubule cells grown in the hormonally defined, serum-free medium demonstrated a slower growth rate, but the functions of cell were enhanced.

• Journal of the Korean Magnetics Society
• /
• v.17 no.4
• /
• pp.166-171
• /
• 2007

We report the magneto-transport properties of an individual single crystalline Bi nanowire grown by a spontaneous growth method. We have successfully fabricated a four-terminal device based on an individual 400-nm-diameter nanowire using plasma etching technique to remove an oxide layer forming on the outer surface of the nanowire. The transverse MR (2496% at 110 K) and longitudinal MR ratios (38% at 2 K) for the Bi nanowire were found to be the largest known values in Bi nanowires. This result demonstrates that the Bi nanowires grown by the spontaneous growth method are the highest-quality single crystalline in the literatures ever reported. We find that temperature dependence of Fermi energy ($E_F$) and band overlap (${\triangle}_0$) leads to the imbalance between electron concentration ($n_e$) and hole concentration ($n_h$) in the Bi nanowire, which is good agreement with the calculated $n_e\;and\;n_h$ from the respective density of states, N(E), for electrons and holes. We also find that the imbalance of $n_e\;and\;n_h$ plays a crucial role in determining magnetoresistance (MR) at T<75 K for $R_T$ and at T<205 K for $R_L$, while mean-free path is responsible for MR at T>75 K for $R_T$ and T>205 K for $R_L$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.4
• /
• pp.458-463
• /
• 2019

Palladium (Pd) is widely used as a catalyst and noxious gas sensing materials. Especially, various researches of Pd based hydrogen gas sensor have been studied due to the noble property, Pd can be adsorbed hydrogen up to 900 times its own volume. In this study, palladium oxide (PdO) nanostructures were grown on Si substrate ($SiO_2(300nm)/Si$) for 3 to 5 hours at $230^{\circ}C{\sim}440^{\circ}C$ using thermal chemical vapor deposition system. Pd powder (source material) was vaporized at $950^{\circ}C$ and high purity Ar gas (carrier gas) was flown with the 200 sccm. The surface morphology of as-grown PdO nanostructures were characterized by field-emission scanning electron microscopy(FE-SEM). The crystallographic properties were confirmed by Raman spectroscopy. As the results, the as-grown nanostructures exhibit PdO phase. The nano-cube structures of PdO were synthesized at specific substrate temperatures and specific growth duration. Especially, PdO nano-cube structrures were uniformly grown at $370^{\circ}C$ for growth duration of 5 hours. The PdO nano-cube structures are attributed to vapor-liquid-solid process. The nano-cube structures of PdO on graphene nanosheet can be applied to fabricate of high sensitivity hydrogen gas sensor.

• Clean Technology
• /
• v.21 no.1
• /
• pp.68-75
• /
• 2015

In this study, we investigated the structure and properties of a highly heat conductive metal-ceramic core-shell CoAl₂O₄@Al micro-composite for heterogeneous catalysts support. The CoAl₂O₄@Al was prepared by hydrothermal surface oxidation of Al metal powder, which resulted in the structure with a high heat conductive Al metal core encapsulated by a high surface area CoAl₂O₄ shell. For comparison, CoAl₂O₄ was also prepared by co-precipitation method and also utilized for a catalyst support. Rh catalysts supported on CoAl₂O₄@Al and CoAl₂O₄ were prepared by incipient wetness impregnation and characterized by N₂ adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO chemisorption, and temperature-programmed reduction (TPR). The properties of catalysts were investigated for glycerol steam reforming reaction for hydrogen production at 550 ℃. Rh/CoAl₂O₄@Al exhibited about 2.8 times higher glycerol conversion turnover frequency (TOF) than Rh/CoAl₂O₄ due to facilitated heat transport through the core-shell structure. The CoAl₂O₄@Al and CoAl₂O₄ also showed some catalytic activities due to a partial reduction of Co on the support, and a higher catalytic activity was also found on the CoAl₂O₄@Al core-shell than CoAl₂O₄. These catalysts, however, displayed deactivation on the reaction stream due to carbon deposition on the catalysts surface.