• Corrosion Science and Technology
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• 제17권3호
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• pp.91-100
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• 2018

Development of biodegradable implants for treatment of complex bone fractures has recently become one of the priority areas in biomedical materials research. Multifunctional corrosion resistant and bioactive coatings containing hydroxyapatite $Ca_{10}(PO_4)_6(OH)_2$ and magnesium oxide MgO were obtained on Mg-Mn-Ce magnesium alloy by plasma electrolytic oxidation. The phase and elemental composition, morphology, and anticorrosion properties of the coatings were investigated by scanning electron microscopy, energy dispersive spectroscopy, potentiodynamic polarization, and electrochemical impedance spectroscopy. The PEO-layers were post-treated using superdispersed polytetrafluoroethylene powder. The duplex treatment considerably reduced the corrosion rate (>4 orders of magnitude) of the magnesium alloy. The use of composite coatings in inducing bioactivity and controlling the corrosion degradation of resorbable Mg implants are considered promising. We also applied the plasma electrolytic oxidation method for the formation of the composite bioinert coatings on the titanium nickelide surface in order to improve its electrochemical properties and to change the morphological structure. It was shown that formed coatings significantly reduced the quantity of nickel ions released into the organism.

• 융복합기술연구소 논문집
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• 제8권1호
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• pp.27-31
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• 2018

The age of electric vehicle is coming. One of the most important problems to be solved for popularization of electric vehicle is fuel economy. To increase fuel economy of electric vehicles, it is necessary to improve the performance of the battery or the car body should be lighter than now. To solve the problem of the car body, change the car body's material to carbon fiber reinforced composites can be an excellent answer. However, the part made from carbon fiber reinforced composites is vulnerable to accidents due to their high brittleness. In this study, ductile silica fume was added into the carbon fiber composites to enhance toughness. To examine this, various amounts and sizes of silica fume were considered and the toughness enhancement was examined by performing tensile tests.

• Composites Research
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• 제29권3호
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• pp.98-103
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• 2016

본 연구에서는 반도체 섬유 강화 복합재료를 이용하여 전자파 흡수 구조를 제작하였다. 두 종류의 반도체 섬유를 사용하여 복합재료를 제작하고, 자유공간 측정 장비를 이용하여 각각의 전자기적 물성을 측정하였다. 두께 최적화 방법으로 두 종류의 단층형 흡수 구조와 한 종류의 이층형 흡수 구조를 설계하였다. 설계한 전자파 흡수 구조를 반도체 섬유 강화 복합재료로 제작하고 그 흡수 성능을 측정하였다. 사용된 두 재료의 유전율은 Cole-Cole plot에 나타내었을 때 무반사 곡선에 가깝지 못하여 높은 흡수 성능을 기대하기 어려웠다. 두 종류의 재료로 제작한 단층형 흡수 구조는 10 GHz 근처에서 각각 -14.2 dB와 -8.8 dB의 흡수 성능을 보였다. 이러한 한계점을 보완할 수 있는 이층형 전자파 흡수 구조는 10 GHz 근처에서 -43.9 dB의 좋은 흡수 성능을 보였다. 반도체 섬유 강화 복합재료로 제작한 이층형 전자파 흡수 구조는 기존의 전자파 흡수 구조에 비해 간단한 제작 과정을 거쳐 좋은 흡수 성능을 갖는 흡수 구조를 얻을 수 있었으며, 상대적으로 더 적은 오차 요인을 갖고 있다.

• 한국분말재료학회지
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• 제8권3호
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• pp.163-167
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• 2001

A bulk porous $CaZrO_3/MgO$ composite with plantinum nano-dispersion was synthesized in air atmosphere through the combination of several in situ reactions, including the pyrolysis of $PtO_2$. A mixture of $CaMg(CO_3)_2$(dolomite), $ZrO_2$, $PtO_2$ and LiF (0.5 wt%, as an additive) was cold isostatically pressed at 200 MPa and sintered at $1100^{\circ}C$ for 2 h. The porous $CaZrO_3/MgO/Pt$ composite ($CaZrO_3/MgO$ : Pt=99 : 1 in volume) had a uniformly open-porous structure (porosity: 56%) with three-dimensional (3-D) network and a narrow pore-size distribution, similarly to the porous $CaZrO_3/MgO$ composites reported before. Catalytic Properties (viz., NO direct decomposition and NO reduction by $C_2H_4$) of the $CaZrO_3/MgO/Pt$ composite were investigated up to $900^{\circ}C$. In the absence of oxygen, the NO conversion rate reached ~52% for the direct decomposition and ~100% for the reduction by $C_2H_4$, respectively. The results suggest the possibility of the porous composite as a multifunctional filter, i.e., simultaneous hot gas-filtering and $de-NO_x$ in one component.

• Composites Research
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• 제36권6호
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• pp.416-421
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• 2023

Multifunctional composite materials capable of both load-carrying and energy functions are promising innovative candidates for the advancement of contemporary technologies owing to their relative feasibility, cost-effectiveness, and optimized performance. Carbon fiber (CF)-based structural batteries utilize the graphitic inherent structure to enable the employment of carbon fibers as electrodes, current collectors, and reinforcement, while the matrix system is an ion-conduction and load transfer medium. Although it is possible to enhance performance through the modification of constituents, there remains a need for a systematic design methodology scheme to streamline the commercialization of structural batteries. In this work, a bi-phasic epoxy-based ionic liquid (IL) modified structural battery electrolyte (SBE) was developed via thermally initiated phase separation. The polymer's morphological, mechanical, and electrochemical characteristics were studied. In addition, the interfacial shear strength (IFSS) between CF/SBE was investigated via microdroplet tests. The results accentuated the significance of considering IFSS and matrix plasticity in designing composite structural batteries. This approach is expected to lay the foundation for realizing smart structures with optimized performance while minimizing the need for extensive trial and error, by paving the way for a streamlined computational design scheme in the future.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1080-1081
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• 2006

In this investigation, $B_4C$ based ceramic composites were fabricated by in-situ reaction hot pressing using $B_4C$, TiC SiC powder as starting materials. The reaction synthesized composites by hot pressing at $1950^{\circ}C$ was found to posses very high relative density. The reaction synthesized $B_4C$ composites comprise $B_4C$, $TiB_2$, SiC and graphite by the reaction between TiC and $B_4C$. The newly formed $TiB_2$ and graphite was embedded both inside grain and at grain boundary $B_4C$. The mechanical properties of reaction synthesized $B_4C-TiB_2-SiC$-graphite composites were more enhanced compared to those of monolithic $B_4C$.

• Carbon letters
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• 제24권
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• pp.90-96
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• 2017

We demonstrated the sensitivity of optically active single-walled carbon nanotubes (SWCNTs) with a diameter below 1 nm that were homogeneously dispersed in cement composites under a mechanical load. Deoxyribonucleic acid (DNA) was selected as the dispersing agent to achieve a homogeneous dispersion of SWCNTs in an aqueous solution, and the dispersion state of the SWCNTs were characterized using various optical tools. It was found that the addition of a large amount of DNA prohibited the structural evolution of calcium hydroxide and calcium silicate hydrate. Based on the in-situ Raman and X-ray diffraction studies, it was evident that hydrophilic functional groups within the DNA strongly retarded the hydration reaction. The optimum amount of DNA with respect to the cement was found to be 0.05 wt%. The strong Raman signals coming from the SWCNTs entrapped in the cement composites enabled us to understand their dispersion state within the cement as well as their interfacial interaction. The G and G' bands of the SWCNTs sensitively varied under mechanical compression. Our results indicate that an extremely small amount of SWCNTs can be used as an optical strain sensor if they are homogeneously dispersed within cement composites.

• Composites Research
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• 제23권2호
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• pp.24-30
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• 2010

니켈-나노분말/에폭시 복합재료의 계면 특성과 소수성을 자체-감지능과 작동기 측정을 위해 평가하였다. 경사형 시편을 사용하여 접촉 저항 및 저항도를 측정하였다. 자기장에서 복합재료의 작동성을 세가지 파형들, 즉, 싸인, 삼각, 그리고 사각파를 사용하여 평가하였다. 균일하지 않은 표면에 존재하는 소수성 영역 때문에 Ni-에폭시 나노복합재료의 어떤 부분은 초소수성보다는 다소 낮은 접촉각인 110도를 가졌다. 동적 접촉각은 정적 접촉각과 경향이 상호 일치함을 보였다. 니켈-나노분말의 고유의 금속성질 때문에 자체 감지를 확인하였으며, 또한 전자기장에 작동 반응을 잘 하였다. 니켈-나노분말/에폭시 복합재료의 최대 및 최적의 성능을 얻기 위해서, 레이져 변위 센서를 사용하여, 파형, 주파수, 그리고 전압의 함수로 작동기의 변위를 평가하였다. 니켈-나노분말/에폭시 복합재료의 작동은 적용된 주파수와 전압의 함수로써 증가하였다. 작동된 복합재료들의 연신율은 전압의 증가에 따라 삼각 혹은 사각파보다 싸인파에서 더욱 빨리 증가하였다.

• Corrosion Science and Technology
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• 제18권5호
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• pp.212-219
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• 2019

This paper reviews recent approaches to develop composite polymer-containing coatings by plasma electrolytic oxidation (PEO) using various low-molecular fractions of superdispersed polytetrafluoroethylene (SPTFE). The features of the unique approaches to form the composite polymer-containing coating on the surface of MA8 magnesium alloy were summarized. Improvement in the corrosion and tribological behavior of the polymer-containing coating can be attributed to the morphology and insulating properties of the surface layers and solid lubrication effect of the SPTFE particles. Such multifunctional coatings have high corrosion resistance ($R_p=3.0{\times}10^7{\Omega}cm^2$) and low friction coefficient (0.13) under dry wear conditions. The effect of dispersity and ${\xi}$-potential of the nanoscale materials ($ZrO_2$ and $SiO_2$) used as electrolyte components for the plasma electrolytic oxidation on the composition and properties of the coatings was investigated. Improvement in the protective properties of the coatings with the incorporated nanoparticles was explained by the greater thickness of the protective layer, relatively low porosity, and the presence of narrow non-through pores. The impedance modulus measured at low frequency for the zirconia-containing layer (${\mid}Z{\mid}_{f=0.01Hz}=1.8{\times}10^6{\Omega}{\cdot}cm^2$) was more than one order of magnitude higher than that of the PEO-coating formed in the nanoparticles-free electrolyte (${\mid}Z{\mid}_{f=0.01Hz}=5.4{\times}10^4{\Omega}{\cdot}cm^2$).

• 대한의용생체공학회:의공학회지
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• 제23권2호
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• pp.139-145
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• 2002

2.2-Bis[P-(2-hydroxy-3-methacryloyloxypropoxyl)phenol]propane (Bis-GMA)는 광중합형 치과용 고분자 복합레진의 다관능성 유기물로 널리 사용되고 있다. Bis-GMA는 두 개의 히드록시기를 가지고 있어서 구강내에서 광중합되는 복합레진의 물흡수를 야기시켜 장기간 점진적으로 심미성이 감소하고 결국엔 복합레진의 기계적 특성까지 저하시키게 된다. 본 연구에서는 최종제품의 내구성과 저장안정성을 향상시키기 위하여 복합레진에 광안정제와 산화방지제를 첨가제로 사용하였다. 먼저 Tinuvin P의 광안정제를 첨가하면 색변화가 큰 것을 볼 수 있었으나 Irganox 245의 산화방지제를 첨가하였을 때 색안정성이 향상됨을 알 수 있었다. 또한 Tinuvin P와 Irganox 245가 동시에 첨가되었을 때 색안 정성이 향상되며 시료의 가속화 실험 전과 가속화 후 간접인장강도와 같은 기계적 성질도 크게 감소되지 않았다. 따라서 치과용 복합레진의 제조에 있어서 첨가제인 Tinuvin P와 Irganox 245가 각각 0.5% 및 0.1% 첨가되었을 때 내구성 및 색안정성이 향상되었으며 나아가 저장 안정성도 향상됨을 확인할 수 있었다.