• 한국분말재료학회지
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• 제23권4호
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• pp.311-316
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• 2016

$Ni(OH)_2$ hollow spheres have been prepared by solvent displacement crystallization using a micro-injection device, and the effect of process parameters such as concentration and the relative ratio of the injection speed of the precursor solution, which is an aqueous solution of $NiSO_4{\cdot}6H_2O$, to isopropyl alcohol of displacement solvent have been investigated. The crystal phases after NaOH treatment are in the ${\beta}-phase$ for all process parameters. A higher concentration of $NiSO_4{\cdot}6H_2O$ aqueous solution is injected by a micro-injection device and bigger $Ni(OH)_2$ hollow spheres with a narrower particle size distribution are formed. The crystallinity and hardness of the as-obtained powder are so poor that hydrothermal treatment of the as-obtained $Ni(OH)_2$ at $120^{\circ}C$ for 24 h in distilled water is performed in order to greatly improve the crystallinity. It is thought that a relative ratio of the injection speed of $NiSO_4{\cdot}6H_2O$ to that of isopropyl alcohol of at least more than 1 is preferable to synthesize Ni(OH)2 hollow spheres. It is confirmed that this solution-based process is very effective in synthesizing ceramic hollow spheres by simple adjustment of the process parameters such as the concentration and the injection speed.

• 공업화학
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• 제10권1호
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• pp.105-111
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• 1999

현재 iron silicide막을 제작하고 있는 방법은 열처리를 수행함으로써 막의 계면 상태가 좋지 않으나 플라즈마를 이용하였을 때는 열처리를 수행하지 않으므로 양질의 막을 얻을 수 있다. 본 실험에서 제작된 막은 Raman 스펙트럼 $250cm^{-1}$에서 나타난 Fe와 Si의 진동모드와 FT-IR에 의해 유기화합물 뿐만 아니라 Fe-Si의 결합이 형성되었음을 확인하였다. 또한 플라즈마의 높은 에너지에 의해 낮은 기판 온도에서 에피택시 성장이 진행되는 동안 iron silicide는 [220]/[202], [115] 등과 같은 격자구조를 갖는 ${\beta}$-상으로 성장하였다. 제조된 막의 band gap은 1.182~1.174 eV의 값을 가지고, 광학적 에너지갭을 3.4~3.7 eV의 값을 나타내었다. 막 내의 유기화합물에 의해 유발되는 Urbach tail과 sub-band-gap 흡수가 관측되었다. 따라서 플라즈마를 이용하여 제작된 막은 단일결정이 성장되어 양질의 박막을 얻을 수 있음을 확인하였다.

• 한국재료학회지
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• 제4권3호
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• pp.319-328
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• 1994

솔-제법에 의한 고분자솔 제조를 위하여 금속 알콕사이드에 $\beta$-diketonate(DKT)기의 유기 리간드를 치환시켜 만든 전구체를 합성한 결과, 가수분해와 축합 반응의 속도 조절이 가능하였고, 이를 이용하여 코팅에 적합한 nm단위의 입자 크기를 갖는 알루미나, 티타니아 솔을 제조하고 그 물성을 파악하였다. 코팅에 적합한 알루미나 솔의 최적조건은 알콕사이드 1몰당 물 1몰, 산 0.3-0.4몰이었다. 티타니아 솔의 제조시는 물/알콕사이드의 몰비가 1이고, 산의 양은 치환수에 따라 달라 1개와 2개 치환된 전구체의 경우 1목의 알콕사이드당 각각 0.25, 0.20몰 이하였다. Dynamic light scattering 장치를 이용하여 제조한 솔의 평균 입자 크기를 측정한 결과 수 nm단위의 미세한 입자를 갖고 있었다. 슬라이드 글라스 위에 코팅하여 $450^{\circ}C$에서 소결한 막을 SEM으로 관찰한 결과 알루미나와 타타니아의 경우 각각 4-4.5$\mu \textrm{m}$, 2-2.5$\mu \textrm{m}$두께의 매끄럽고 균열이 없는 막이 형성되었음을 알 수 있었다. 이때의 입자 크기는 TEM사진을 통하여 알 수 있었으며 티타니아의 경우 수 nm에서 최대 30nm, 알루미나는 1-2nm이하 심지어 수 $\AA$정도의 입자들로 이루어졌음을 관찰하였다. 또한 회절무늬 분석 결과 알루미나는 $\gamma$구조, 티타니아는 anastase결정임을 알 수 있었다.

• 헤리티지:역사와 과학
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• 제36권
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• pp.267-297
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• 2003

The plain coarse pottery from the Unjeonri Bronze Age relic sites in the Cheonan, Korea were studied on the basis of clay mineralogy, geochemistry and archaegeological interpretations. For the research, the potteries are utilized at the analysis for 6 pieces of plain coarse potteries. Color of the these potteries are mainly light brown, partly shows the yellowish brown to reddish brown. The interior, surface and inside of the pottery appear as different colors in any cases. Original source materials making the Unjeonri potteries are used of mainly sandy clay soil with extreme coarse grained irregularly quartz and feldspar. The magnetic susceptibility of the Unjeonri pottery range from 0.20 to 1.20. And the Unjeonri soil's magnetic susceptibility agree almost with 0.20 to 1.30. In the same magnetization of soil and pottery, the results revealed that the Unjeonri soil and low material of pottery are same produced by identical source materials. The Unjeonri potteries and soil are very similar patterns with all characteristics of soil mineralogy, geochemical evolution trend. The result seems to be same relationships between the behavior and enrichment patterns on the basis of a compatible and a incompatible elements. Consequently, the Unjeonri potteries suggest that made the soil to be distributed in the circumstance of the relic sites as the raw material are high in a greater part. In the Unjeonri soil, the kaolinite is common occurred minerals. However, in the Unjeonri pottery, the kaolinite was not detected in all broken pieces. The kaolinite was presumed to destroy crystal structure during the firing processes of over $550^{\circ}C$. The quartz is phase transition from ${\alpha}$-quartz to ${\beta}$-quartz at $573^{\circ}C$, but the Unjeonri pottery did not investigated any phase transition evidences of quartz. The chorite was detected within the mostly potteries and soils. As the results, the Unjeonri potteries can be interpreted by not experiencing a firing temperature over $800^{\circ}C$. The colloidal and cementing materials between the quartz and low materials during the heating did not exist in the internal part of the potteries. An any secondary compounds by heating does not appear within the crack to happen during the dry of the pottery. The hyphae group are kept as it is with the root tissue of an organic matters to live in the swampy land. In the syntheses of all results, the general firing condition to bake and make the Unjeonri pottery is presumed from $550^{\circ}C$ to $800^{\circ}C$. However, the firing condition making the Unjeonri pottery can be different firing temperature partially in one pottery. Even, the some part of the pottery does not take a direct influence on the fire.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.1-33
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• 1997

The objective of this study was to analyze the in vitro and in vivo corrosion products of low and high copper amalgams. The four different types of amalgam alloy used in this study were Fine cut, Caulk spherical, Dispersalloy, and Tytin. After each amalgam alloy and Hg were triturated according to the directions of the manufacturer by means of the mechanical amalgamator(Amalgam mixer. Shinhung Co. Korea), the triturated mass was inserted into a cylindrical metal mold which was 12mm in diameter and 10mm in height. The mass was condensed by 150Kg/cm compressive force. The specimen was removed from the mold and aged at room temperature for about seven days. The standard surface preparation was routinely carried out by emery paper polishing under running water. In vitro amalgam specimens were potentiostatically polarized ten times in a normal saline solution at $37^{\circ}C$(potentiostat : HA-301. Hukuto Denko Corp. Japan). Each specimen was subjected to anodic polarization scan within the potential range -1700mV to+400mV(SCE). After corrosion tests, anodic polarization curves and corrosion potentials were obtained. The amount of component elements dissolved from amalgams into solution was measured three times by ICP AES(Inductive Coupled Plasma Atomic Emission Spectrometry: Plasma 40. Perkim Elmer Co. U.S.A.). The four different types of amalgam were filled in occlusal and buccal class I cavities of four human 3rd molars. After about five years the restorations were carefully removed after tooth extraction to preserve the structural details including the deteriorated margins. The occlusal surface, amalgam-tooth interface and the fractured surface of in vivo amalgam corrosion products were analyzed. In vivo and in vitro amalgam specimens were examined and analyzed metallographically by SEM(Scanning Electron Microscope: JSM 840. Jeol Co. Japan) and EDAX(Energy Dispersive Micro X-ray Analyser: JSM 840. Jeol Co. Japan). 1. The following results are obtained from in vitro corrosion tests. 1) Corrosion potentials of all amalgams became more noble after ten times passing through the in vitro corrosion test compared to first time. 2) After times through the test, released Cu concentration in saline solution was almost equal but highest in Fine cut. Ag and Hg ion concentration was highest in Caulk spherical and Sn was highest in Dispersalloy. 3) Analyses of surface corrosion products in vitro reveal the following results. a)The corroded surface of Caulk spherical has Na-Sn-Cl containing clusters of $5{\mu}m$ needle-like crystals and oval shapes of Sn-Cl phase, polyhedral Sn oxide phase. b)In Fine cut, there appeared to be a large Sn containing phase, surrounded by many Cu-Sn phases of $1{\mu}m$ granular shapes. c)Dispersalloy was covered by a thick reticular layer which contained Zn-Cl phase. d)In Tytin, a very thin, corroded layer had formed with irregularly growing Sn-Cl phases that looked like a stack of plates. 2. The following results are obtained by an analysis of in vivo amalgam corrosion products. 1) Occlusal surfaces of all amalgams were covered by thick amorphous layers containing Ca-P elements which were abraded by occlusal force. 2) In tooth-amalgam interface, Ca-P containing products were examined in all amalgams but were most clearly seen in low copper amalgams. 3) Sn oxide appeared as a polyhedral shape in internal space in Caulk spherical and Fine cut. 4) Apical pyramidal shaped Sn oxide and curved plate-like Sn-Cl phases resulted in Dispersalloy. 5) In Tytin, Sn oxide and Sn hydroxide were not seen but polyhedral Ag-Hg phase crystal appeared in internal space which assumed a ${\beta}_l$ phase.