• 한국작물학회지
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• 제43권4호
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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.

• 식물분류학회지
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• 제35권4호
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• pp.313-335
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• 2005

식물규소체는 토양과 물에 용해된 규소가 이산화규소($SiO_2$)의 형태로 식물체내의 여러 기관 또는 표피세포에 축적되면서 형성되어 식물의 성장과 발달에 중요한 영향을 미치는 것으로 밝혀지고 있어, 식물의 규소체에 관한 연구가 시행되고 있다. 따라서 본 연구에서는 한국산 사초과 (Cyperaceae) 식물 13속 228종 중, 12속 136종의 잎의 표피형에서 밝힌 규소체의 형태를 검토하여 정리하였다. 그 결과 한국산 사초과 식물은 규소체의 모양에 따라 2 그룹으로 구분되었다. 제 1 그룹은 원추형(conical body)의 규소체를 나타내고, 골풀아재비속(Rhynchospora), 검정방동산이속(Fuirena), 너도고랭이속(Scleria), 사초속(Carex)과 황새풀속(Eriophorum)이 이에 속한다. 제 2 그룹은 규소체의 모양이 원추형을 중심으로 많은 위성형을 보이며, 방동산이속(Cyperus), 올챙이골속(Scirpus), 바늘골속(Eleocharis), 하늘지기속(Fimbristylis), 파대가리속(Kyllinga), 모기골속(Bulbostylis)과 세대가리속(Lipocarpha.)이 속한다.

• 한국세라믹학회지
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• 제29권9호
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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.

• 한국세라믹학회지
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• 제50권6호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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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.

• 한국세라믹학회지
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• 제26권5호
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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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• 제10권2호
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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.

• 한국분말재료학회지
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• 제1권2호
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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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• 제35권3호
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• pp.283-305
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• 1992

Phytolith는 식물 세포내, 세포벽 또는 세포간에 축적되는 현미경적 구조의 무기염류의 구조물을 통칭하는 용어이다. 그러나 현재까지의 연구들이 주로 규소의 축적에 의하여 형성되는 식물규소체를 중심으로 수행되었기 때문에 현재는 식물규소체를 지칭하는 용어로 흔히 사용되고 있다. 식물규소체는 화본과 식물의 분류에 유용한 형질이며, 미소화석으로 그 효용성이 토양학, 고생태학, 고고학 등의 분야에서 입증되었다. 또한 근자에는 발암물질로의 가능성도 제시되고 있다. 본 문에서는 식물규소체의 특성과 이들의 분석 그리고 식물학적 이용과 더불어 여타 분야에서의 이용 가능성을 소개하고자 한다.

• 한국세라믹학회지
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• 제53권2호
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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.