• Progress in Superconductivity
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• 제13권1호
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• pp.7-11
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• 2011

조성경사법을 이용하여 LMO/IBAD-MgO template 상에 EDDC 증착법을 이용하여 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 초전도 박막을 증착하였다. 테이프 형상의 기판상에 길이방향으로 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 박막의 조성비가 연속적으로 변하는 샘플을 얻을 수 있었고, 비접촉 Hallprobe를 이용하여 임계전류를 측정한 결과 조성비에 대응하는 연속적인 임계전류분포를 측정할 수 있었다. 본 조성비 영역 중 Sm:Ba:Cu = 1.01:1.99 :4.87의 조성비에서 최대의 임계전류를 보였다. 이 조성비에서 SmBCO 박막표면에 전체적으로 roof tile 형상의 결정립들이 관찰되었으며 국소적으로 2차상들이 관찰되었다. 조성 경사법을 이용하면 광범위한 조성비영역에서 신뢰도 높은 초전도특성, 결정배향성, 박막표면 형상 등을 조사할 수 있을 것으로 예상된다.

• 한국융합학회논문지
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• 제12권12호
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• pp.145-151
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• 2021

Ti Gr4에 TPS 법을 이용하여 HA 코팅을 수행하여 코팅층에 대한 물리적특성 및 생체적합성을 판단하여 의료용 부품으로서의 활용성에 대한 평가를 하였다. 직경 25mm Ti Gr4 합금 시험편을 기계가공 후 #120, #400, #1,000 샌드페이퍼 및 바렐 연마로 표면을 연마를 하여 ASTM F1185-88로 HA 코팅은 한 후 HA 코팅층의 두께, 표면조도, 강도 및 접착력 측정 시험과 세포독성 시험을 하였다. Ti Gr4에 대한 HA 코팅 결정도는 75.51%, Ca/P 비는 1.67의 값을 얻을 수 있었다. HA 코팅층의 두께는 Ti 소재의 표면거칠기가 거칠수록 증가하고, 코팅의 강도 및 접착력은 시험장치의 지그 형상, 에폭시 성분, 크로스헤드 속도 등에 따라 변화가 있을 것으로 예측된다. 세포독성 시험은 Grade 3의 반응성으로 적합한 것으로 나타났다. 본 실험 결과 TPS에 의한 Ti Gr4 소재의 HA 코팅 두께 향상과 골융합을 촉진이 가능할 것으로 확인되어 인체삽입용으로 상용화가 가능할 것으로 판단된다.

• 대한금속재료학회지
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• 제48권4호
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• 한국환경과학회지
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• 제14권7호
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• pp.699-709
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• 2005

This study aimed at improving the $TiO_2$ photocatalytic degradation of HA. In this study, the Degradation of Humic Acid using Jeju Scoria Coated with $WO_3/TiO_2$ in the presence of UV irradiation was investigated as a function of different experimental condition : photocatalyst dosage, $Ca^{2+}\;and\;HCO_{3}_{-}$ addition and pH of the solution. Photodegradation efficiency increased with increasing photocatalyst dosage, the optimum catalyst dosage is 2.5 g/L and Photodegradation efficiency is maximized to $WO_3/TiO_2=3/7$. This indicates that $WO_3$ retains a much higher Lewis surface acidity than $TiO_2,\;and\;WO_3$ has a higher affinity for chemical species having unpaired electrons. The addtion of cation($Ca^{2+}$) in water increased the photodegradaion efficiency. But the addtion of $HCO_{3}^{-}$ ion in water decreased a photodegradation efficiency. Photodegradation efficiency increased with decreasing pH < pzc, the electrostatic repulsion between the HA and the surface of $TiO_2$ decreased.

• Macromolecular Research
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• 제13권4호
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• pp.306-313
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• 2005

Surface modified nanofillers are often used as curative-cum reinforcing agents for functional polymers. The polymer nanofiller interaction depends on the curative systems used. In the present study the carboxylic group of the carboxylated nitrile elastomer participated in the reaction with Zn-ion coated nanosilica filler producing a type of ionomeric elastomer. The interaction at the molecular level thus produced a high modulus vulcanizate. In this case, the S and MBT system, as curative, had an edge over the MDA and DPG curative system. Interfacial adhesion was enhanced in the presence of Zn-ion-coated nanosilica filler associated with dynamic mechanical behavior. The inferior properties obtained in the case of the MDA and DPG curative system were due to the decreased reactivity of the silica surface, thus reducing interfacial adhesion.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1087-1090
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• 2008

Present research is devoted to the development of optical sheet intended to be used inside LCD Backlight unit in order to improve output axial Luminance. It deals with refractive by nature optical sheet having relief embossed top surface (microlenses array). Patterned reflecting layer can be coated on flat bottom surface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2008년도 추계학술대회 초록집
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• pp.126-126
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• 2008

코팅도막의 열이동특성에 대해 연구하였다. 소재의 양면 및 단면으로 코팅한 후 열전도도와 방사율을 측정하여 코팅도막의 열방출특성을 비교, 분석하였다．

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 추계학술대회 초록집
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• pp.170-170
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• 2009

코팅도막의 열이동특성에 대해 연구하였다．소재의 양면 및 단면으로 코팅한 후 열전도도와 방사율을 측정하여 코팅도막의 열방출특성을 비교, 분석하였다.

• Archives of Plastic Surgery
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• 제37권4호
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• pp.340-345
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• 2010

Purpose: Recently, bioceramics have become popular as a substitute graft material for reconstruction of bony defect after trauma or tumor surgery. Among the bioceramic materials, hydroxyapatite (HA) is favored due to its biocompatibility. HA scaffold is composed of the interconnected reticular framework, macropores and micropores. Macropores play an important role in cell migration, nutrients supply and vascular ingrowth. On the other hand, a number of micropores less than $10{\mu}m$ form an irregular surface on HA scaffolds, which prevents the osteoblast from adhering and proliferating on the surface of HA scaffold. Methods: In this study, three different groups were designed for comparison. In the first group (group A), conventional method was used, in which HA pellet was applied without surface pretreatment. The second group (group B) was given a HA pellet that has been coated with crystalline HA solution prior to application. In the third group (group C), the same method was used as the second group, where the pretreated HA pellet was heated ($1250^{\circ}C$, 1 hour) before application. Osteoblast-like cells ($2{\times}10^4$/mL) were scattered onto every pellet, then they were incubated in 5% $CO_2$ incubator at $37^{\circ}C$ for twelve days. During the first three days, osteoblast cells were counted using the hemocytometer daily. ALP activity was measured on the 3, 6, 9 and 12 culture days using the spectrophotometer. Results: Under SEM, group A showed a surface with numerous micropores, and group B revealed more rough crystal surface. Group C revealed a fused crystal appearance and flattened smooth surface. In proliferation and ALP activity of osteoblast cells, group C showed better results compared to group B. Group A which lacks pretreatment of the surface showed less osteoblast proliferation and ALP activity than group C, but showed better results than group B. Conclusion: We found that crystallized HA with heat treatment method enhances the osteoblasts proliferation and differentiation on the surface of HA pellets.

• Archives of Plastic Surgery
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• 제36권3호
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• pp.247-253
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• 2009

Purpose: Hydroxyapatite(HA) has been widely used due to its chemical similarity to bone and good biocompatibility. HA is composed of macropores and micropores. Too much irregularities of the micropores are ineffective against the adhesion and proliferation of osteoblast. Many efforts have been tried to overcome these drawbacks. HA crystal coating on the irregular surface of HA scaffold, crystallized HA, is one of the method to improve cell adhesion. Meanwhile, the collagen has been incorporated with HA to create composite scaffold that chemically resembles the natural extracellular matrix components of bone. The authors proposed to examine the effect of collagen - coated crystallized HA on the adhesion and proliferation of osteoblast. Method: HA powder containing $10{\mu}m$ pore size was manufactured as 1 cm pellet size. For the making crystallized HA, 0.1 M EDTA solution was used to dissolve HA powder and heated $100^{\circ}C$ for 48 hours. Next, the crystallized HA pellets were coated with collagen (0.1, 0.5, and 1%). The osteoblasts were seeded into HA pellets and incubated for the various times (1, 5, and 9 days). After the indicating days, methylthiazol tetrazolium (MTT) assay was performed for cell proliferation and alkaline phosphatase (ALP) activty was measured for bone formation. Result: In SEM study, the surface of crystallized HA pellet was more regular than HA pellet. MTT assay showed that the proliferation of osteoblasts increased in a collagen dose - dependent and time - dependent manner and had a maximum effect at 1% collagen concentration. ALP activity also increased in a collagen dose - dependent manner and had a highest effect at 1% collagen concentration. Conclusion: These data showed that crystallization and collagen coating of HA was effective for osteoblast proliferation and ALP activity. Therefore, our results suggest that crystallized - HA scaffold with collagen coating is may be a good strategy for tissue engineering application for bone formation.