• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.205-208
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• 1998

Silica bodies (phytoliths) are becoming of wide use for pedology, archaeology, paleobotany and paleoecology in botany. This study investigated morphological differences of silica bodies in the lamina of wild, indica type, and japonica type rice. Phytoliths in the epidermis of lamina showed noticeable difference among tested plants. Besides, there were also significant differences in the shape and distribution of the silica bodies around stomata and trichomes. Silica bodies in the lamina of the rice plants could be used to classify subspecies of Oryza genus.

• Korean Journal of Plant Taxonomy
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• v.35 no.4
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• pp.313-335
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• 2005

Many plants take up soluble silica from the soil, and they deposit in plant tissues. Silica bodies are most commonly found in the leaf epidermis. Silica body is important factor in growth and development of plant. It help to maintain rigidity in stem and linear leaves, and its content may be correlated with resistance to fungal disease. In this study, several morphologically distinctive forms of silica bodies on Cyperaceae in Korea are recognized, which are eventually classified into two groups. Silica body type of first group (Rhynchospora, Fuirena, Scleria, Carex, Eriophorum) is A-type, which is conical in shape. Silica body type of second group (Cyperus, Scirpus, Eleocharis, Fimbristylis, Kyllinga, Bulbostylis, Lipocarpha) is B-type, which is conical in shape with numerous satellite body. These types are consistent enough to use as characters in taxonomic studies within genus. Silica body type may be associated with habitat: the species in dry region have A-type, whereas the species in wet region have B-type. These results suggested that shapes and presence or absence of silica body might be valuable to systematic analysis.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.719-728
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• 1992

ZrO2/Al2O3-Mullite composites were prepared by infiltration of the silica sol to the porous ZrO2/Al2O3 bodies. The porous ZrO2/Al2O3 bodies for infiltration were fabricated using ZrO2 (20wt%)/Al2O3 composite powders synthesized by the emulsion-hot kerosene drying method. The preparation of silica sols was conducted by the hydrolysis-peptization of an alcoholic TEOS solution. When ZrO2/Al2O3-Mullite and ZrO2/Al2O3 composites were sintered at 1$650^{\circ}C$ for 4 hrs, both of them showed an excellent sinterability. As the amount of mullite added in the composites increased, the ratio of the tetragonal phase of zirconia to the monoclinic phase at the room temperature became higher. It was known that values of the fracture toughness of the ZrO2/Al2O3-Mullite composites were about 5.48 MPa.m1/2 much larger than that of the ZrO2/Al2O3 system.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.416-422
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• 2013

Cullet-loess tile bodies are successfully fabricated using cullet, loess, hollow microspheres, and sintering additives (borosilicate glass frit, boric acid, or fumed silica) as starting materials. The effects of the additive composition and sintering temperature on the sintered density and flexural strength of the cullet-loess tile bodies are investigated. The sintered density of the cullet-loess tile bodies increases with an increase in the sintering temperature as a result of the enhanced densification of pore walls through the viscous flow of a liquid phase formed from the glass frit and sintering additives. The flexural strength of the cullet-loess tile bodies increases with increases in the sintering temperature and the cullet content in the starting composition. A maximal flexural strength of 40 MPa is obtained in cullet-loess tile bodies sintered with glass frit at $800^{\circ}C$ in air.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.428-433
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• 2000

The consolidation behavior of multicomponent particles prepared by the flame hydrolysis deposition process is examined to identify the effects of Si substrate temperature. To fabricate multi-component particles, a vapor-phase ternary mixture of $SiCl_4(100 cc/min),\;BCl_3(30cc/min)\;and\;POCl_3,(5cc/min)$ was fed into a coflow diffusion oxy-hydrogen flame burner. The doped silica soot bodies were deposited on silicon substrates under various deposition conditions. The surface temperature of the substrate was measured by an infrared thermometer. Changes in the chemical states of the doped silica soot bodies were examined by FT-IR(Fourier-transformed infrared spectroscopy). The deposited particles on the substrate were heated at $1300^{\circ}C$ for 3h in a furnace at a heating rate of 10K/min. Si-O-B bending peak has been found when surface temperature exceeds $720^{\circ}C$. Correspondingly, the case with substrate temperatures above loot produced good consolidation result.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.637-644
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• 1989

Beta-sialon powder(Z=1) was synthesized by the simultaeous reduction and nitridation of the mixed powders of Hadong kaolin and silica. Silicon hydroxide was prepared from Si-alkoxide by a hydrolysis method and amorphous silica was obtained from the calcination of the prepared silicon hydroxide. Hadong kaolin was mixed with both the silicon hydroxide and amorphous silica, respectively. The average particle size was 4${\mu}{\textrm}{m}$ and the morphology of particle was rod-like and equiaxed in the case of beta-sialon powder prepared form Hadong kaolin and silicon hydroxide(COMPOSITION A), whereas the average particle size was 3${\mu}{\textrm}{m}$ and the morphology of particle was equiaxed in the case of beta-sialon powder prepared from Hadong kaolin and amorphous silica(COMPOSITION B). The synthesized beta-sialon powders were hot-pressed at 175$0^{\circ}C$ for 2 hours under 30 MPa in a nitrogen atmosphere after YAG composition(8wt%) was added to these powders as a sintering agent. The hot-pressed specimens were annealed a 140$0^{\circ}C$ for 4 hours in a nitrogen atmosphere. The mechanical properties of sintered bodies were investigated in terms of M.O.R., fracture toughness and hardness. The measured values are as follows. COMPOSITION A : M.O.R. 508MPa, KIC 3.5MN/m3/2, hardness 13.6GPa. COMPOSITION B : M.O.R. 653MPa, KIC 5.4MN/m3/2, hardness 13.5GPa.

• Journal of Microbiology and Biotechnology
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• v.10 no.2
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• pp.233-237
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• 2000

As part of a continuing investigation to identify free radical scavengers from the fruit bodies of basidiomycetes, we isolated two p-terphenyl compounds, designated as PAl and PA2l, from cethanolic extract of the fruit body of Pasillus panuoides. The methanolic extract was processed by ethyl acetate extraction and silica gel column chromatography to yield two active fraction. PAl was obtained from one of the fractions through Sephadex LH-20 and silica gel column chromatographies and reverse-phase HPLC. The other fraction was purified by Sephadex LH-20 and reverse-phase column chromatographies to produce PA2. The compounds PA1 and PA2 were identified as leucomentin-4 and leucomentin-2, respectively, on the basis of various spectroscopic analyses. These compounds exhibited strong inhibitory activities against lipid peroxidation in rat liver microsomes with IC_{50}$ values of 0.10 and $0.06{\;}\mu\textrm{g}ml$, respectively.

• Journal of Powder Materials
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• v.1 no.2
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• pp.135-144
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• 1994

Silicon carbide powder was prepared from mixtures of Sangdong silica sand and carbon black by SHS (Self propagating High temperature Synthesis) method which utilizes magnesiothermic reduction of silica. In the powder preparation process, the reacted powder was leached by chloric acid to remove the magnesium oxide and was subsequently roasted to remove free carbon. The impurities were mostly eliminated by hot acid treatment. The resultant SiC powder showed the mean particle size of 0.22 ${\mu}{\textrm}{m}$ and the specific surface area of $66.55 m^2/g$. The SiC powder was mixed with 1 wt% of boron and of carbon to increase densification rate. The mixed powder was pressed and sintered pressurelessly at $2100^{\circ}C$ for 30 min in argon gas. The sintered body showed the hardness of $2550 kg{\cdot}f/mm^2$ and the fracture toughness, KIC of $3.47 MN/m^{3/2}$.

• Journal of Plant Biology
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• v.35 no.3
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• pp.283-305
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• 1992

Phytoliths (plant stones) mean all types of mineral deposition formed in or between plant cells. However, most of the researches on the phytoliths so far have been focused on the opaline silica bodies (silicified phytoliths) formed by grasses. Therefore, the phytolith is usually refered to opaline silica body in a narrow sense. Phytoliths are very useful in grass classification, and their usefulness as microfossils is also proved in several other fields, including soil science, paleoecology, and archaeology. Recently attention has been paid to the possibility that they might function as carcinogen. The purpose of this review is to present an overview of the nature and analysis of phytoliths and their applications in botany as well as other fields of sciencess.encess.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.246-252
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• 2016

Complex designed silica-based ceramic cores were fabricated by ceramic injection molding. Slow heating rate (0.2K/min) for debinding restrained bloating on the surface of ceramic cores. To investigate effect of sintering conditions on mechanical properties of ceramic cores, green bodies were sintered at temperatures in a range from $1150^{\circ}C$ to $1400^{\circ}C$ for various dwelling times (6 h to 48 h). Sintering above $1300^{\circ}C$ for 12 h and dwelling time over 24 h at $1200^{\circ}C$ reduce the flexural strength and increase the linear shrinkage of ceramic cores. Cristobalite, formed by high sintering temperature or long dwelling time, induces reduction of mechanical properties due to its phase transformation, which is accompanied by volume contraction and microcracking. Ceramic core sintered at $1200^{\circ}C$ for 12 h endured wax patterning and shell molding, and was manufactured successfully.