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생체활성 유리 골 시멘트의 응결 및 수산화 아파타이트 형성
임형봉,김철영,Lim, Hyoung-Bong,Kim, Cheol-Young 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.11
Hardening and hydroxyapatite(HAp) formation behavior of the bioactive cements in the system of $CaO-SiO_{2}-P_{2}O_{5}$ glasses and the corresponding glass-ceramics were studied. DCPD (Dicalcium Phosphate Dihydrate: $CaHPO_4{\cdot}2H_2O$) and DCPA (Dicalcium Phosphate Anhydrous: $CaHPO_4$) were developed when the prepared glass and glass-ceramic powders were mixed with three different solutions. The DCPD and DCPA transformed to HAp when the cement was soaked in Simulated Body Fluid (SBF), and this HAp formation strongly depended on the releasing capacity of $Ca^{2+}$ ions from the cements. The glass-ceramic containing apatite showed fast setting, but no HAp formation was observed because no $Ca^{2+}$ ions were released from this glass-ceramics. The compressive strength of the cements increased with reaction time in SBF until all DCPD and DCPA transformed to HAp.
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치과 임플란트용 지르코니아-알루미나 복합체의 생 가공 및 경 가공 특성
임형봉,당동욱,이기주,조원승,Lim, Hyung-Bong,Tang, Dongxu,Lee, Ki-Ju,Cho, Won-Seung 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.2
The green and hard machining characteristics of dental ceramics are of great interest to dental industry. The green bodies of TZP/$Al_2O_3$ composites were prepared by the cold isostatic pressing, and machined on the CNC lathe using PCD (polycrystalline diamond) insert under various machining conditions. With increasing nose radius of PCD insert, surface roughness initially increased due to increased cutting resistance, but decreased by the onset of sliding fracture. The lowest surface roughness was obtained at spindle speed of 1,300 rpm and lowest feed rate. Hard bodies were prepared by pressureless sintering the machined green bodies at several temperatures. The grinding test for sintered hard body was conducted using electroplated diamond bur with different grit sizes. During grinding, grain pull out in the composite was occurred due to thermal expansion mismatch between the alumina and zirconia. The strength of the composite decreased with alumina contents, due to increased surface roughness and high monoclinic phase transformed during grinding process. The final polished samples represented high strength by the elimination of a phase transformation layer.
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유리 및 결정화 유리 골 시멘트에서 DCPD의 형성 및 수산화 아파타이트로의 전환
임형봉,김철영,Lim, Hyung-Bong,Kim, Cheol-Young 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.1
The glass in the system of CaO-$SiO_2-P_2O_5$ and the corresponding glass-ceramics are prepared for bone cements and the behaviors of the hardening and hydroxyapatite formation were studied for the glass and glass-ceramic powders. The glass crystallized into apatite, $\alpha$-wollastonite and $\beta$-wollastonite depending on the glass composition when they were heat-treated at $950^{\circ}C$ for 4 h. A DCPD (dicalcium phosphate dihydrate : $CaHPO_4{\cdot}2H_2O$) was developed when the prepared glass and glass-ceramic powders were mixed with 3M-$H_3PO_4$ solution. The DCPD (Ca/P=1.0) transformed to HAp (Ca/P=1.67) when the bone cement was soaked in simulated body fluid (SBF), and this HAp formation strongly depended on the releasing capacity of $Ca^{2+}$ ions from the glass and glass-ceramic cements. The glass-ceramic bone cement containing $\alpha$-wollastonite crystals showed faster transformation of DCPD to HAp than other glass-ceramics containing $\alpha$- and $\beta$-wollastonite crystals. No hydroxyapatite was observed when the glass-ceramic bone cement containing apatite crystals (36P6C) was soaked in SBF even for 1 month, because no $Ca^{2+}$ ion can be released from the stable apatite crystals.
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다양한 산화물들이 리튬규산염 유리의 결정화에 미치는 영향
김철민,임형봉,김용수,김세훈,오경식,김철영,Kim, Chul-Min,Lim, Hyung-Bong,Kim, Youg-Su,Kim, Se-Hoon,Oh, Kyung-Sik,Kim, Cheol-Young 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.4
Glass-ceramics based on lithium disilicate($Li_2Si_2O_5$) are prepared by heat-treatment of glasses in a system of $SiO_2-Li_2O-K_2O-Al_2O_3$ with different compositions. The crystallization heat-treatment was conducted at the temperature range of $700{\sim}900^{\circ}C$ and samples were analyzed by XRD and SEM. Mechanical properties were determined by a Vicker's hardness and 4 point bending strength. When $SiO_2/Li_2O$ ratio increased, cristobalite and tridymite crystals showed more predominate than lithium disilicate crystals. Increase in $Al_2O_3$ contents in the glass suppressed crystallzation of lithium disilicate crystals. Increase in ZnO, $B_2O_3$ contents in the glass decreased crystallization temperature of lithium disilicate crystals, and increased mechanical properties because of the reduction of the lithium disilicate crystal size.
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김철영,임형봉,조남권,곽희열,Kim, Cheol-Young,Lim, Hyong-Bong,Cho, Nam-Kwon,Kwak, Hee-Youl 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.9
The sealing technique between a glass tube and a copper heat pipe in an evacuated tube solar collector is studied. In this study two different sealing techniques, such as flame method and furnace firing, are examined. After the sealing of a copper to a glass, the oxidation state of the copper and its bonding morphology were examined by SEM and XRD. Its oxidation was retarded by coating of borate solution on the copper, and $Cu_2O(cuprite)$ turned into CuO(tenorite) with increase in a firing temperature and firing time. Porous structure was found in the oxide layer when CuO formed. The best sealing morphology was observed when the thickness of the oxidation layer was less than $20{\mu}m$. The sealing technique performed in a furnace was promising and the satisfactory result was obtained when the sample was fired at $950^{\circ}C$ for 5 min under $N_2$ atmosphere. Annealing procedure is recommended to remove the stress left at the bonding zone.
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알칼리토 금속산화물이 함유된 붕규산염계 유리를 이용한 용액 중 Cr^(6+) 이온 제거 기구
백일희,임형봉,김철영 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.3
The hexavalent chromium ions in wastewater are highly toxic chemicals even at low concentrations. It causes serious diseases, such as cancer, skin disease, digestive trouble et. al. In this study, Cr^(6+) ions were removed by using borosilicate glasses. Various glasses system with different compositions were prepared and then reacted in a solution contaning Cr^(6+) ions. After the reaction, the concentration of the Cr^(6+) ions remained in the solution was measured by ICP-OES. The reacted surface of the glasses was also analyzed by using a XRD, SEM, and EDS. When Na_2O-RO-SiO_2-B_2O_3 (RO=MgO, CaO, SrO, BaO) glasses were reacted with a solution containing Cr^(6+) ions, the optimum removal efficiency of Cr^(6+) ions was observed in the BaO glass. Ba^(2+) ions leached out of these glasses combine with Cr^(6+) ions in a solution to form BaCrO_4 crystals on the glass surface. In this manner, the Cr^(6+) ions can be removed from the solution. It is conceivable that Ba2+ ions are reacted with Cr^(6+) ions in a solution immedeately after leaching out of the glasses. The pH of the solution for optimum removal of Cr^(6+) ions were 3.0~5.0.
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