• 한국재료학회지
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• 제17권9호
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• pp.480-483
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• 2007

Hydroxyapatites were prepared by the different $SiO_2$ addition at $1450^{\circ}C$ for 2h. With the increase of $SiO_2$ addition, microstructure, bulk density, porosity, mechanical strength of $hydroxyapatite/{\beta}-TCP$ composite were investigated. When the sintered HAp contained 1 wt% $SiO_2$, the each properties of the HAp were increased. But the excess addition of $SiO_2$ content above 1wt% the each property were decreased. This results were due to the ${\beta}-TCP$ phase. The ${\beta}-TCP$ phase appeared at 3 wt% $SiO_2$ addition and the ${\beta}-TCP$ phase was enhanced by the $SiO_2$ increasing.

• 한국분말재료학회지
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• 제11권5호
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• pp.421-426
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• 2004

The microstructure and mechanical property of hot-pressed $Al_2O_3/Cu$ composites with a different temperature for atmosphere changing from H$_{2}$ to Ar have been studied. When atmosphere-changed from H$_{2}$ to Ar gas at 145$0^{\circ}C$, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when atmosphere-changed at low temperature of 110$0^{\circ}C$ the composite showed more homogeneous microstructure, higher fracture strength and smaller deviation in strength. Based on the thermodynamic consideration and microstructural analysis, it was interpreted that the Cu wetting behavior relating to the formation of CuAlO$_{2}$ is probably responsible for strong dependence of microstructure on atmosphere changing temperature. The reason for a strong sensitivity of fracture strength and especially of its deviation to atmosphere changing temperature was explained by the microstructural inhomogeneity and by the role of CuAlO$_{2}$ phase on the interfacial bonding strength.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.333-334
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• 2006

The objective of this study is to fabricate a piezoelectric composite consisting of a piezoelectric ceramic and a high toughness material and to evaluate their electromechanical properties for high force actuator applications. The mixture of the piezoelectric material, PMNZT, and high toughness material, $ZrO_2$, exhibited high piezoelectric properties as well as good mechanical fracture resistance. Up to 2 vol% of $ZrO_2$ in PMNZT matrix, piezoelectric $d_{33}$ coefficient was above 400 pC/N, being 80% of that for the original PMNZT, and the toughness showed twice of the PMNZT. When the volume fraction of the $ZrO_2$ was above 5%, however, the piezoelectric coefficient became abruptly decreased and it approached 20% of value for the PMNZT.

• Composites Research
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• 제33권4호
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• pp.213-219
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• 2020

최근 플라스틱 폐기물로 인한 환경 문제가 이슈화되면서 친환경 소재에 대한 관심이 점점 증가하고 있으며, 이에 따라 천연섬유를 활용한 복합재의 연구가 지속적으로 이루어지고 있지만 친환경 복합재의 강도나 계면 접착력에 대한 연구가 많이 부족한 실정이다. 복합재료의 강도나 계면 접착력을 향상시키는 방법들 중 한 가지 방법은 나노 입자를 첨가하여 기계적 물성을 향상시키는 방법이 있다. 본 연구에서는 기존에 사용되는 고가의 나노소재를 대체할 수 있는 친환경적이면서 경제적인 천연섬유를 해초로부터 추출하여 첨가제를 제조하고, 복합재료의 제조 및 기계적 특성평가를 수행하였다. 시험결과 제조한 첨가제가 복합재료의 인장, 굽힘, 충격 등의 물성 향상에 효과가 있을 뿐만 아니라 친환경성과 경제성도 가지고 있어 후속연구를 통해 다양한 분야에 적용할 수 있을 것이라 기대된다.

• Steel and Composite Structures
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• 제17권1호
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• pp.105-121
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• 2014

A fundamental limitation of steel structures is the decrease in their load-bearing capacity at high temperatures in fire situations such that structural members may require some additional treatment for fire resistance. In this regard, this paper evaluates the structural stability of fire-resistant steel, introduced in the late 1999s, through tensile coupon tests and proposes some experimental equations for the yield stress, the elastic modulus, and specific heat. The surface temperature, deflection, and maximum stress of fire-resistant steel H-section columns were calculated using their own mechanical and thermal properties. According to a comparison of mechanical properties between fire-resistant steel and Eurocode 3, the former outperformed the latter, and based on a comparison of structural performance between fire-resistant steel and ordinary structural steel of equivalent mechanical properties at room temperature, the former had greater structural stability than the latter through $900^{\circ}C$.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.102.2-102.2
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• 2012

Different layers of zirconium nitride (ZrN) and hydroxyapatite (HA) coatings were prepared on cp Ti substrate for biomedical applications. The main idea is to improve the mechanical strength as well as the biocompatibility of the coating. ZrN is known for its high mechanical strength, corrosion resistance. HA is well known for its biocompatibility properties. Hence, in this study, both materials were coated on a cp Ti substrate with bottom layer with ZrN for good bonding with substrate and the top layer with HA for induce bioactivity. Middle layer was formed by a composite of HA and ZrN. Detail analyses of the layered coatings for its structural, morphological, topographical properties were carried out. Then the mechanical property of the layered coatings was analyzed by nanoindentation. Biomimetic growths of apatite on the functionally graded coatings were determined by simulated body fluid method. This study provides promising results to use this kind of coatings in biomedical field.

• 대한기계학회논문집A
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• 제35권8호
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• pp.877-882
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• 2011

스태빌라이저는 선박, 자동차 및 비행기 등에서 과도한 동요를 막고 자세를 안정시키는 장치를 말한다. 본 연구에서 스태빌라이저 링크 POM-GF25%인 복합재료와 금속을 사용하여 제조하였다. 스태빌라이저 강도 평가를 위하여 인장, 압축 및 볼스터드 빠짐으로 실시하였으며, 모두 기준을 만족하였다. 4가지 형태의 로드에서, 널링된 로드가 가장 큰 강도를 나타내었으며, 금속제를 대체할 수 있을 것으로 판단된다. 또한 사출 금형의 재해석으로 스태빌라이저 링크 본체의 형상을 개선하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.43-48
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• 2000

Composite materials have been increasingly used in automotive and aircraft industries, naturally leading to active researches on the materials. The carbon-epoxy composite is selected to study its thermal characteristics. During multiple thermal cycles composed of repeated cooling and heating variations of elastic constants are investigated to understand thermal effects on the carbon-epoxy composite. In this investigation longitudinal resonance method and flexural resonance method was used to characterize. The values of $E_1$ show small amount of increases depending on number of cycles of the thermal fatigue processes whereas values of $G_13$ do not indicate noticeable changes. Also, in cases of $E_2$ and $G_23$ their values decrease to a certain extend in initial stages after applications of thermal fatigue processes. However, the number of cycles of the applied thermal fatigue processes does not seem to affect their values.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1181-1186
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• 2008

Insulators which are used in the domestic electrical industries are mostly depended on importation from some advance countries. Even though insulators which are made of ceramic material have been mostly used domestically, the ratio of usage on composite insulators is recently being increased because of difficulties in manufacturing and high cost regarding ceramic stuffs. In this research, we are trying to develop the composite insulators which are very efficient in insulation regardless of the matter of weight. Even though the technique of manufacturing composite insulator are quite generalized worldwide at the moment, one of the most important issue is to keep security on the know-how that an ingredient of insulated material named 'SF6 gas' is included. Therefore, The aim of this paper is to improve the bonding force and air tight property between two components of composite insulator, Flange and FRP Tube.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.21-24
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• 2003

In general, to enhance physical properties of PET-layered silicate nanocomposites $(P_{et}LSNs)$, it has been well known that the organic modifiers should introduce into gallery regions. However, the organic modifiers in$(P_{et}LSNs)$ may result in thermal decomposition by melt processing at high temperature, and it necessarily lead to deteriorate various physical properties of final products. Therefore, in this study, $(P_{et}LSNs)$ excluding and including organic modifiers were prepared by solution method $(S-P_{et}LSNs_{eom} and S-P_{et}LSNs_{iom})$ and we (focused on the effects of the organic modifiers in $P_{et}$ LSNs with exfoliation structure on the crystallization behaviors, the optical transparency, the thermal stability and the mechanical property. The absence and existence of organic modifiers in $S-P_{et}LSNs_{eom} and S-P_{et}LSNs_{iom}$ were investigated by EA and TGA, and nano-structure of silicate layers in $S-P_{et}LSNs$ was evaluated by using WXRD, SAXS and TEM. $S-P_{et}LSNs_{eom} and S-P_{et}LSNs_{iom}$ were mixed with neat PET as masterbatches by melt method $(M-P_{et}LSNs_{eom} and M-P_{et}LSNs_{iom})$, and also neat PET was mixed with organically modified layered silicates (OLS) by conventional direct melt method $(D-P_{et}LSNs) at 270^{\circ}C$. As results, it was found that $M-P_{et}LSNs_{eom}, M-P_{et}LSNs_{iom}, and D-P_{et}LSN$ showed a exfoliated structure and exhibited faster crystallization rate, better thermal stability and mechanical property than those of neat PET due to the dispersed and detaminated silicate layers in PET matrix. Whereas, considering organic modifiers effect, $M-P_{et}LSNs_{eom} and D-P_{et}LSN$ exhibited slower crystallization rate, poorer optical, thermal and mechanical properties, in comparison to $M-P_{et}LSNs_{eom}> due to the thermal decomposition of organic modifier in $D-P_{et}LSNs$ during melt method.