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RISS 인기검색어
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- 저자 : Hyung-Bong Lim(임형봉) (검색결과 3 건)
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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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