• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.21 no.2
• /
• pp.70-74
• /
• 2011

[ $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ]ceramics was investigated for the application to SOFC ceramic supporter with high porosity and mechanical strength. $ZrO_2$ powder was prepared by combustion method with glycine using the solution of $ZrO(NO_3)_2{\cdot}2H_2O$ dissolved into deionized water and calcination at $800^{\circ}C$ Porous $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics was prepared by sintering the mixture of prepared $ZrO_2$ powder, dolomite and carbon black at $1200{\sim}1400^{\circ}C$ for 1 h. The open porosity ofthe $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics sintered at $1300^{\circ}C$ was over 30 % and increased linearly with the amount of carbon black. The crystal structure of $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics consisted of single cubic phase. The open pore of this ceramics was connected continuously and distributed well on the whole. This ceramics sintered at $1300^{\circ}C$ showed the porosity from 32 to 55 % and mechanical strength from 90 MPa to 30 MPa with increasing the content of added carbon black.

• Korean Journal of Plant Resources
• /
• v.29 no.4
• /
• pp.385-392
• /
• 2016

This research was performed to develop seminal propagation method of Saururus chinensis (Lour.) Baill. by conducting a rigorous germination study. Well-selected seeds were dry-stored at 4 ± 1.0℃ during the experiment. To study dormancy type, non-stored seeds were analyzed by embryo observation, germination test and detecting for any difficulties in seed coat to absorb moisture. Then to improve germination, seeds were submerged for 24 hours in a solution of varying concentrations containing one of plant growth regulators and minerals. According to research, fleshly matured seeds had an undifferentiated embryo and had a low germination rate below 5%. In addition, water submersion led to moisture absorption, embryo in the seeds grew and germinated so it was deemed morphophysiological dormant seeds. Percent germination (PG) and germination energy (GE) was greatly improved by soaking in plant growth regulators and minerals for 24 hours. Especially, 500 ㎎/L GA₃ treatment resulted in the highest GE as 46.1%. KNO₃ meaningfully improved PG (54.3∼57.7%) at 10∼20 mM but effect of minerals on germination acceleration as GE were negatively impacted in all concentrations.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.4
• /
• pp.645-650
• /
• 1998

Alumina- and yttria-coated SiC powder was prepared by the surface-induced precipitation method, and sintered properties of silicon carbide prepared from this powder were investigated. After a well dispersion of SiC powders in the aqueous solution of $Al_2(SO_4)_3$ and $Y_2(SO_4)_3$, the mixed precursors of aluminum hydroxide, aluminum carbonate, yttrium hydroxide, and yttrium carbonate were precipitated on the surfaces of SiC particles through the hydrolysis reaction of urea. SiC specimens with alumina and yttria exhibit, 97.8% of theoretical density after the sintering at $1900^{\circ}C$ for 2 hrs. During annealing at $2000^{\circ}C$, $\beta$longrightarrow$\alpha$ phase transformation of SiC had taken place and resulted with a rodlike microstructure. Toughness of sintered SiC was enhanced by crack deflection around the rodlike grains. In case of annealing less than that of 3 hr, the fracture toughness of SiC was slightly improved with increasing the amount of sintering aid. However, annealed specimens for a long time showed constant fracture toughness even though the amount of sintering aid increased. It is resulted that the main factor for toughening in annealed SiC for a long time is the pullout effect of rodlike grains during the propagation of cracks, and the amount of sintering aids is less effective on the fracture toughness of SiC.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.195-195
• /
• 2016

Titanium and its alloys are widely used as implants in orthopedics, dentistry and cardiology due to their outstanding properties, such as high strength, high level of hemocompatibility and enhanced biocompatibility. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element, such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}-stabilizer$ and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Silicon (Si) and magnesium (Mg) has a beneficial effect on bone. Si in particular has been found to be essential for normal bone and cartilage growth and development. In vitro studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. The aim of this study is to research Si and Mg doped hydroxyapatite film formation by plasma electrolytic oxidation. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. Each alloy was anodized in solution containing typically 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at room temperature. A direct current power source was used for the process of anodization. Anodized alloys was prepared using 270V~300V anodization voltage at room. A Si and Mg coating was produced by RF-magnetron sputtering system. RF power of 100W was applied to the target for 1h at room temperature. The microstructure, phase and composition of Si and Mg coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

• Journal of Embryo Transfer
• /
• v.10 no.1
• /
• pp.53-63
• /
• 1995

The effects of different protein sources (serum vs bovine serum albumin), growth factors (EGF and PDGF) and co-culture with various type of somatic cel1s (BOEC, MEF and BRL) on the in vitro development of in vitro matured / in vitro fertilized bovine oocytes were examined, and the viability of frozen/thawed embryos derived from IVM /IVF was examined. Cell numbers of blastocysts were also counted. In Experiment 1, CR$_1$aa with serum was superior to CR$_1$aa with BSA in producing morulae plus blastocysts from IVM /IVF oocytes(24.4% vs 30.4%, p>0.05). In Experiment 2, more morulae plus blastocysts(42.3%) were produced in CR$_1$aa containing long /ml EGF than in the control CR$_1$aa(33.3%). In Experiment 3, 2- to 8-cell embryos derived from IVM /IVF oocytes were randomly allotted to one of 4 culture groups : a) CR$_1$aa ; b) CR$_1$aa + ing /ml PDGF ; CR$_1$aa + Sng /ml PDGF ; CR$_1$aa + lOng /ml PDGF ; culture resulted in 21.3, 51.2, 41.4 and 45.9%(p<0.05), respectively, developing into morulae and blastocysts. In Experiment 4, 0 and Sng /ml PDGF added to CR$_1$aa coculture with BRL or BOEC yielded 47.5, 42.5, 33.8 and 41.6% morulae and blastocysts, respectively. In Experiment 5, the proportion of embryos into morulae and blastocysts was highest in CR$_1$aa with MEF coculture group(50.9%) compared to any other group(CR$_1$aa, 22.3%; CR$_1$aa+BRL, 32.9%; CR$_1$aa+BOEC, 33.8%, p>0.05). In Experiment 6, survival rate of blastocysts produced by in vitro fertilization when cryoprotectant was removed in 0.7M glycerol+0.7M sucrose and 0.7M sucrose solution for 10 min. after thawing at 2$0^{\circ}C$ (Exp. H, 58.8%) was slightly higher than when cryoprotectant was removed 10%, 6.7% and 3.3% glycerol for 10 min. after thawing at 37$^{\circ}C$ (Exp. I, 54.3%). These study indicate that growth factors and somatic cell co-culture can increase the proportion of embryos that develop into morulae and blastocysts without an increase in the cell number and frozen /thawed method employed this experiment was not different.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.20 no.2
• /
• pp.69-73
• /
• 2010

The microstructural change of the $Sm_{0.5}Sr_{0.5}CoO_3$ (SSC) electrode for a cathode material of solid oxdie fuel cells (SOFCs) deposited by the electrostatic spray deposition (ESD) technique was characterized. Samarium chloride hexahydrate $(SmCl_3{\cdot}6H_2O)$, strontium chloride hexahydrate $(SrCl_2{\cdot}gH_2O)$, cobalt nitrate hexahydrate $(Co(No_3)_2{\cdot}6H_2O)$ as starting materials and methyl alcohol as solvent were used to make precursor solution. The suitable porous SSC films for a cathode of SOFCs were deposited on Si substrate and it is observed that the microstructure was strongly dependent on processing parameters such as deposition time, substrate temperature, and applied voltage. Scanning Electron Microscope (SEM) and X-ray Diffractometer (XRD) measurement were used to investigate the microstructure and crystallinity of the SSC films. The ESD technique is shown to be an efficient method in which the SOFCs' cathode film can be fabricated with the desired phases and microstructure.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.3
• /
• pp.219-225
• /
• 2000

The spinel structured $LiMn_2O_4$was obtained by two consecutive heat treatment on xerogel; the first heat treatment was at $150^{\circ}C$ and the second at $350^{\circ}C$ was obtained by sol-gel process using an aqueous solution of lithium hydroxide and manganese acetate. The synthesized $LiMn_2O_4$ by the sol-gel process showed a discharge capacity of 88~56 mAh/g after 15 cycles in Li/lM $LiClO_4$(in PC)/$LiMn_2O_4$at a current density of 0.25 mA/$\textrm{cm}^2$ and the voltage ranged 3.5 V to 4.3 V. For the second heat treatment above $350^{\circ}C$, $Mn_2O_3$was formed as a by-product during the synthesis of $LiMn_2O_4$. The heat treatment at $500^{\circ}C$, for example, showed a lower discharge capacity 81~47 mAh/g, after the 15 charge/discharge cycles. The lower capacity was due to the increment of $Mn^{3+}$ ion and this phenomenon was in agreement with the Jahn-Teller distortion.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.4 no.2
• /
• pp.199-209
• /
• 1994

$PbTiO_3$ thin films were prepared on soda-lime-silica slide glasses, Si-wafer and sapphire substrate by the dip-coating of precursor solution. As starting materials, titanium tetra iso-propoxide and lead acetate trihydrate were used. Then acetylacetone was added to prepare stable sol. The effect of the parameters such as viscosity and composition of sol were investigated. The optical transmittance at visible range, refractive index, IR spectra were measured in varying compositions, thickness and heat treatment temperature. The crystallization of $PbTiO_3$ films were measured by using XRD and SEM. Diffusion of compositions from slide glass to thin film were investigated by using EDX, too. These sols not precipitated for 20 days. Transmittance of $PbTiO_3$ films at visible range were decreased with the increase of thickness and heat treatment temperatures, and were exhibited flat spectra. Pyrochlore type appeared in the films on slide glass and perovskite type appeared in the films on Si-wafer or sapphire at $600^{\circ}C$. Perovskite crystals transformed to $PbTi_3O_7$ phase at $800^{\circ}C$.

• Journal of Bio-Environment Control
• /
• v.13 no.3
• /
• pp.135-142
• /
• 2004

The objective of this study was carried out to determine which method is effective for improving seed germination in carrot and onion among osmotic or solid matrix priming. Seeds were osmotic primed with -0.5 MPa polyethylene glycol 8000 (PEG) solution and solid matrix primed with Micro Cel E (seed, Micro Cel E, and water mixed with the ratio of 4.0：2.0：8.0 by weight for carrot, and the ratio of 4.0：1.2：5.0 for onion at $20^{\circ}C$ for 4 days). Seeds were rapidly absorbed water after osmotic priming and solid matrix priming treatment. The moisture content of solid matrix primed seeds was lower than that of osmotic primed seeds in carrot and onion. Osmotic priming and solid matrix priming did not influenced on increasing of percent germination, but $T_{50}$ of treated seeds was shorter than those of untreated seeds at four temperature regimes. The effects of osmotic or solid matrix priming in reducing the $T_{50}$ was greater when the seeds were germinated at $15^{\circ}C$ than at $25^{\circ}C$ and $30^{\circ}C$ temperature. Solid matrix primed seeds germinated faster than osmotic primed seeds at all temperature in both carrot and onion. After priming, surface-dried seeds germinated faster than dried-back seeds in carrot and onion. Emergence speed of carrot and onion seeds was faster than untreated seeds by osmotic priming or SMP treatment although the final emergence percentage was not significantly influenced. On the other hand, early growth was not significantly influenced by osmotic priming or SMP treatment of carrot and onion seeds.

• Applied Biological Chemistry
• /
• v.47 no.4
• /
• pp.379-383
• /
• 2004

For the elucidation of substrate specificity to the brown copra meal by Bacillus sp. ${\beta}-mannanase.$, the enzymatic hydrolysate after 24 hr of reaction was heated in a boiling water bath for 10 min, and then centrifuged to remove the insoluble materials from hydrolysates. The major hydrolysates composed of D.P 5 and 7 galactosyl mannooligosaccharides. For the separate of galactosyl mannooligosaccharides, the supernatant solution of 150 ml was put on a first activated carbon column. The column was then washed with 5 l of water to remove mannose and salts. The oligosaccharides in the column were eluted by a liner gradient of $0{\sim}30%$ ethanol, at the flow rate of 250 ml per hour. The sugar composition in each fraction tubes was examined by TLC and FACE analysis. The combined fraction from F3 was concentrated to 30 ml by vacuum evaporator. Then put on a second activated carbon column. The oligosaccharides in the column were eluted by a liner gradient of $0{\sim}30%$ ethanol (total volume: 5 l), at the flow rate of 250 ml per hour. The eluent was collected in 8 ml fraction tubes, and the total sugar concentration was measured by method of phenol-sulfuric acid. The major component of F2 separated by 2nd activated carbon column chromatography were identified $Gal^3Man_4(6^3-mono-{\alpha}-D-galactopyranosyl-{\beta}-mannotetraose)$. To investigate the effects of brown copra meal galactomannooligosaccharides on growth of Bifidobacterium longum, B. bifidum were cultivated individually on the modified-MRS medium containing carbon source such as $Gal^3Man_4$, compared to those of standard MRS medium.