소 뼈로부터 제조한 다공형 하이드록시아파타이트 세라믹스의 생체친화 특성

이종국,고영화,이난희,Lee, Jong-Kook,Ko, Young-Hwa,Lee, Nan-Hee 한국결정성장학회 2012 한국결정성장학회지 Vol.22 No.3

소뼈를 하소하여 천연 하이드록시아파타이트 분말을 얻은 다음, $1100^{\circ}C$ 및 $1200^{\circ}C$로 상압 소결하여 기공율이 각각 35 % 및 18 %인 다공성 하이드록시아파타이트를 제조한 후 이들 시편의 생체친화성을 평가하였다. 골아세포의 성장속도과 세포독성의 유무에 따라 평가되는 생체친화성은 MG-63 세포의 부착능과 분화되어 증식되는 세포의 수로 측정하였다. in vitro에서 세포 반응을 관찰한 결과 소뼈로부터 제조된 하이드록시아파타이트 시편은 독성이 없고 생체 친화성이 좋은 시편이었다. 세포배양 1일 후부터 하이드록시아파타이트 표면에 세포가 부착되었고, 세포배양 후 3일 후에는 핵 주위로 세포질이 퍼져나갔으며, 5일 후에는 부착된 세포의 수가 크게 증가하였다. 배양 초기에는 밀도에 관계 없이 세포의 부착능이 유사하였지만, 세포 배양 시간이 증가하면서 기공율이 높은 시편에서 세포의 부착 및 성장이 더 활발하게 진행되었다. Natural hydroxyapatite powder was obtained from the calcination of bovine bones and its porous compacts were fabricated by pressureless sintering at 1100 and $1200^{\circ}C$ for 1h. To evaluate and compare their biocompatibility with porosity, we investigated the support of osteoblast cells growth and cytotoxicity using the MG-63 cell line model in vitro. Sintered hydroxyapatite ceramics have a porous microstructure with a relative density of 65 % at $1100^{\circ}C$ and 82 % at $1200^{\circ}C$. Cells adherence to the surface of hydroxyapatite ceramics was observed in a day after the cell culture, and the spreading of cytoplasm around the nucleus was shown after 3 day cell culture. Most of cells were extended to the surface of hydroxyapatite through the wide area. Cell viability was nearly the same till 3 days culturing. But the rate of cell growth is higher in the specimen sintered at $1100^{\circ}C$ than that of $1200^{\circ}C$. It indicates that the porosity is an important factor to enhance the cell viability in the porous hydroxyapatite ceramics derived from bovine bones.

실버 페이스트의 치밀화 및 비저항에 미치는 소결조제와 프릿의 영향

이종국,박성현,양권승,Lee, Jong-Kook,Park, Sung-Hyun,Yang, Gwon-Seung 한국재료학회 2008 한국재료학회지 Vol.18 No.5

The effect of sintering aids and glass-frit on the densification and resistivity of silver paste was investigated in an effort to enhance the sintered density and electrical conductivity of the silver electrode. To prepare Pb-free silver paste for use at low sintering temperatures, two commercial silver powders ($0.8\;{\mu}m$ and $1.6\;{\mu}m$ in size) and 5wt.% lab-synthesized nanoparticles (30-50 nm in size) as a sintering aids were mixed with 3 wt.% or 6 wt.% of glass frit ($Bi_2O_3$-based) using a solvent and three roll mills. Thick films from the silver paste were prepared by means of screen printing on an alumina substrate followed by sintering at $450^{\circ}C$ to $550^{\circ}C$ for 15 min. Silver thick films from the paste with bimodal particles showed a high packing density, high densification during sintering and low resistivity compared to films created using monomodal particles. Silver nanoparticles as a sintering aid enhanced the densification of commercial silver powder at a low sintering temperature and induced low resistivity in the silver thick film. The glass frit also enhanced the densification of the films through liquid phase sintering; however, the optimum content of glass frit is necessary to ensure that a dense microstructure and low resistivity are obtained, as excessive glass-frit can provoke low conductivity due to the interconnection of the glass phase with the high resistivity between the silver particles.

콜로이드 Ag 나노입자 합성시 계면활성제의 영향

이종국,최남규,서동석,Lee Jong-Kook,Choi Nam-Kyu,Seo Dong-Seok 한국재료학회 2005 한국재료학회지 Vol.15 No.5

Silver nanoparticles were synthesized by chemical reduction method from aqueous silver nitrate solution ana hydrazine as a reduction agent. The morphology, particle size and shape were dependent on the mixing method, reaction temperature and time, molar ratio of hydrazine and silver nitrate, the kind of surfactant, and the addition of surfactant. The stability of the colloidal silver was achieved by the adsorption of surfactant molecules onto the particle. Silver nanoparticles have a characteristic absorption maximum at 430 nm under UV irradiation. It was found that the colloid was nanometer m size and formed very stable dispersion of silver. The Ag nanoparticles obtained showed the spherical shape with the size range of 10-30 nm.

저온 열처리에 의한 Y-TZP 미세조직의 변화

이종국,김환,Lee, Jong-Kook,Kim, Hwan 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.6

The phase transformation of Y-TZP by low temperature aging treatments and its related behaviors of crack formation were investigated. The kinetics of phase transformation was greatly dependent on the amounts of Y2O3, grian size and microstructures of sintered body. The phase transformation happened to start at specimen surface and near the pore in the first place, where the change of strain energy during the phase transformation was small and the water vapor that accelerated phase transformation easily diffused.

CeO$_2$ 도핑에 의한 불규칙 입자형상의 이트리아 안정화 지르코니아 제조

이종국,강현희,김영정,김환,Lee, Jong-Kook,Kang, Hyun-Hee,Kim, Young-J.,Kim, Hwan 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.12

Yttria-stabilized zirconia ceramics with irregular grain shapes and curved grain boundaries was prepared by ceria doping. The amount of ceria doped into zirconia compacts by a dipping method were at range of 2 to 20 mol% Irregular grain shapes and curved grain boundaries were formed only inspecimens doped with more than 8mol% cerial. Ceria-doped specimens showed large grain size and low sintered density compared with pure yttria-stabilized zirconia which was due to the increase in the contents of stabilizer and cubic phase. The amount of doped ceria was larger on the surface than the inside regions and therefore mi-crostructure and phase on the surface were different from those in the inside regions. Transgranular frac-ture mode was observed ion ceria doped specimens due to irregular large grain sizes.

천연 및 인공원료로부터 제조한 생체친화형 하이드록시아파타이트 세라믹스

이종국,고영화,이난희,Lee, Jong-Kook,Ko, Young-Hwa,Lee, Nan-Hee 한국재료학회 2012 한국재료학회지 Vol.22 No.6

Hydroxyapatite (HA) is well known as a biocompatible and bioactive material. HA has been practically applied as bone graft materials in a range of medical and dental fields. In this study, two types of dense hydroxyapatite ceramics were prepared from natural bones and synthetic materials. The biocompatibility of HA ceramics for supporting osteoblast cell growth and cytotoxicity using an in vitro MG-63 cell line model were respectively evaluated. Artificial hydroxyapatite shows relative density of 93% with 1-2 ${\mu}m$ after sintering, but a hydroxyapatite compact derived from bovine bone has low sintered density of 85% with a small content of MgO. Irrespective of the starting raw materials, both types of sintered hydroxyapatite displayed similar biocompatibility in the tests. FE-SEM observations showed that most MG-63 cells had a stellar shape and formed an intercellular matrix containing fibers on sintered HA. The cells were well attached and grown over the HA surface, indicating that there was no toxicity.

상압소결에 의하여 제조된 SiC-AlN 복합체에서의 고용체 형성과 미세구조

이종국,김덕준,김환,Lee, Jong-Kook,Kim, Duk-Jun,Kim, Hwan 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.7

Formation of Solid Solution and Microstructure in Processureless sintered SiC-AlN compo-site using oxides as a sintering aid at 185$0^{\circ}C$ and 195$0^{\circ}C$ Regardless of SiC/AlN ratio in composition most of sintered specimens showed he complex structure mixed with 2H solid solution and SiC particles. High sintering temperature and large AlN content in starting composition enhanced the formation of 2H solid solution in sintered specimen 2H solid solution showed the spherical shape and core-rim structure. AlN content in the core is higher than that in the rim but SiC content . The size of 2H solid solution on fracture showed the transgranular fracture mode compared with the dispersed SiC particles which showed the intergranular fracture mode.

PVA 흡착에 의한 안정한 콜로이드 지르코니아 졸의 합성

이종국,문기동,김환,Lee, Jong-Kook,Moon, Gi-Dong,Kim, Hwan 한국결정성장학회 1995 韓國結晶成長學會誌 Vol.5 No.2

PVA를 첨가하여 제조한 collloidal $ZrO_2$ 졸에 있어서 입자의 분산성 및 입성장에 미치는 PVA의 영향을 고찰하였다. 적정량의 PVA를 첨가하여 제조된 colloidal 졸은 균일한 흡착층의 형성으로 입자간의 응집이 효과적으로 억제된 분산이 양호한 안정된 졸이었으며 이러한 분산성은 PVA가 $ZrO_2$ 일차입자 표면에 흡착층이 형성되어 입성장을 억제하기 때문이었다. $ZrO_2$ 입자의 핵생성은 수화반응 초기에 대부분 일어났으며, 숙성 시간 에 따라 판상의 단사정상 입자가 성장하였는데 PVA의 첨가량이 증가할수록 입성장 속도와 반응수율이 감소하였다. PVA 첨가에 의해 잘 분산된 현탁액으로부터 제조된 충진체는 입자가 고르게 배열되고 응집체간에 형성된 기공이 균일하였다. A stable suspension with a colloidal $ZrO_2$ particle was prepared by an adsorption of PV A and investigated to the effects of PV A on the dispersion and particle growth within suspension. With a suspension added the optimum concentration of PYA (about 500 ppm in this study), it was shown the property of a stable sol due to the formation of adsorbed PV A layer on surface and the reduction of an agglomeration among the particles. Most of nucleation in colloidal $ZrO_2$ were occured in the early stage of hydrolysis reaction and the plate-like monoclinic $ZrO_2$ particle were grown with an aging time. The rate of particle growth and yield for a reaction were decreased with an addition of PV A. The compact prepared from well- dispersed suspension by an addition of PV A was contained the homogeneous particle arrangement and pore distribution.

저온 열처리에 의한 Y-TZP 분말의 등온 상전이

이종국,김환,Lee, Jong-Kook,Kim, Hwan 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.8

The ifluence of transformability and stabilized effects in tetragonal phase on the isothermal phase transformation of Y-TZP at low temperature were investigated. The transformability of Y-TZP powders were gradually increased with calcination temeprature and reached maximum at critical temperature, but when the Y-TZP powders were calcined above critical temperature, transformability of Y-TZP were gradually decreased with increasing calcination temperature. It was concluded that maximum transformability was appeared because particle size effects decreased and constrain effects increased with calcined temperature. The isothermal phase transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amounts of transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amount of transformed monoclinic phase during aging decreased with increasing constrain effects. From these results, the mechanism of isothermal phase transformation and degradation behaviors at low temperature in Y-TZP was concluded that occurred by decreasing of constrain effects due to stress relaxation at grian boundary.

CMBOK Framework을 이용한 건설 프로젝트 핵심관리요소의 도출

이종국,이현수,Lee Jong-Kook,Lee Hyun-Soo 한국건설관리학회 2004 건설관리 : 한국건설관리학회 학회지 Vol.5 No.1

본 연구는 건설 프로젝트 관리의 틀로서 이전 연구에서 제시된 CMBOK Framework을 이용하여 각 관리요소간의 상호작용을 분석하고, 이들 상호작용현상의 중심에 있는 12가지의 핵심관리요소를 추출하여 제시하였다. 또한, 이들 핵심관리요소에 대한 실제 건설 프로젝트 관리현장의 사례를 통하여 핵심관리요소로서의 활용 타당성을 검증하였다. 이러한 핵심관리요소의 건설산업 활용을 통하여 건설 프로젝트 관리 업무의 과학화와 효율성 향상이 기대된다. Based on the CMBOK (Construction Project Management Body of Knowledge) Framework previously developed in early study by the authors in conjunction with use of some questionnaire surveys and personal interviews with industry professionals, the authors analyze interactions among the entities in the CMBOK framework for the extraction of pivotal entities of construction project management and identify twelve pivotal entities in construction project management, then verify the existence of twelve pivotal entities in real construction project management of construction company and checked the validity of the entities with a real case of interaction phenomenon. This research provides the construction industry with a starting point for improving construction project management efficiency by identifying the pivotal entities.