• Elastomers and Composites
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• 제46권2호
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• pp.125-131
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• 2011

일정한 길이로 분쇄한 케냐프섬유를 일정한 비율로 PP수지에 복합화하여 섬유의 함량에 따른 기계적특성을 조사하였다. 케냐프 섬유의 함량이 증가할수록 인장강도, 굴곡탄성률, 충격강도, 비중, 열변형온도가 증가하는 경향을 나타내었으나 신장률, 굴곡강도, 용융유동지수는 감소하는 경향을 나타내었다. 기계적물성증가의 원인은 섬유와 PP간의 계면접촉면적의 증가와 섬유간의 연결간섭으로 고찰되었다. 케냐프섬유내에 존재하는 증발성추출물질이 PP와 의 계면접착에 있어서 감소에 영향을 미치는 것으로 고려된다.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.9-19
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• 2020

기능성 나노박막을 손상 없이 목표기판으로 옮기는 전사 기술은 나노박막 기반의 차세대 응용 제품 개발을 위한 초석이다. 본 논문에서는 최근 나노박막 전사의 연구 동향을 박막-기판 계면의 박리 원리에 따라 습식 식각 전사, 전기화학적 박리, 기계식 전사 방법 세 가지로 분류하여 간단하게 살펴볼 것이다. 더 나아가, 손쉽고, 기판 재활용이 가능하며, 광범위한 적용 가능성을 가지고 있어 유망 기술로 간주되는 기계식 전사 방법에 대하여 파괴 역학적 관점에 초점을 맞추어 다룰 것이다. 마지막으로, 나노박막의 기계식 전사 방법의 기술 성숙도를 향상시키기 위한 향후 도전 과제와 방향성에 대하여 고찰하고자 한다.

• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.801-809
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• 2013

We investigate sensitivity and limit of detection (LOD) of trace copper (Cu) metal using pristine carbon nanotube (CNT) and acidified CNT (ACNT) electrodes. Squarewave based anodic stripping voltammetry (SWASV) is used to determine the stripped Cu concentration. Prior to performing the SWASV measurements, its optimal conditions are determined and with that, effects of potential scan rate and $Cu^{2+}$ concentration on stripping current are evaluated. The measurements indicate that (1) ACNT electrode shows better results than CNT electrode and (2) stripping is controlled by surface reaction. In the given $Cu^{2+}$ concentration range of 25-150 ppb, peak stripping current has linearity with $Cu^{2+}$ concentration. Quantitatively, sensitivity and LOD of Cu in ACNT electrode are 9.36 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb, while their values are 3.99 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb with CNT electrode. We evaluate the effect of three different water solutions (deionized water, tap water and river water) on stripping current and the confirm types of water don't affect the sensitivity of Cu. It turns out by optical inspection and cyclic voltammetry that superiority of ACNT electrode to CNT electrode is attributed to exfoliation of CNT bundles and improved interfacial adhesion occurring during oxidation of CNTs.

• Composites Research
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• 제29권5호
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• pp.269-275
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• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• 한국건축시공학회지
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• 제4권2호
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• pp.143-149
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• 2004

The recycle of domestic waste concrete is, however, still in an early stage, and it has been only partially being used for the road fillers. As a counter-plan of activating recycled concrete, we have confirmed the hydration possibility of the waste concrete powder from the experiment on recycling the aggregate powder since 2000. Though that study, we have known that the strength is increasing when the baking time is longer, and baking temperature maintain in $700^{\circ}C$. Also, the quality is lowered because of the fine aggregate powder which has a bad influence on flowability & compression strength by adhesion of mortar on the aggregate face. Therefore, mortar and interfacial separation of aggregate are large in proper quality for concrete recycling is expected that affect. The purpose of this study is to investigate effective aggregate separation and to determine the most suitable production method controlling the duration of baking time for recycled cement from the compressive strength, X-ray diffraction and ingredient analysis test.

• Macromolecular Research
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• 제13권3호
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• pp.223-228
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• 2005

In the present work, a low-density polyethylene (LDPE) composite, filled with Zn-ion coated structural silica encapsulated with the diglycidyl ether of bisphenol-A (DGEBA), was synthesized using the conventional melt-blending technique in a sigma internal mixer. The catalytic activity of the Zn-ions (originating from the structural silica) towards the oxirane group (diglycidyl ether of bisphenol-A (DGEBA): encapsulating agent) was assessed by infrared spectroscopy. Two composites, each with a filler content of $2.5 wt\%$ were developed. The first one was obtained by melt blending the Zn-ion coated structural silica with LDPE in a co-rotating sigma internal mixer. The second one was obtained by melt blending the same LDPE, but with DGEBA encapsulated Zn-ion coated structural silica. Epoxy resin encapsulation of the Zn-ion coated structural silica resulted in its having good interfacial adhesion and a homogeneous dispersion in the polymer matrix. Furthermore, the encapsulation of epoxy resin over the Zn-ion coated structural silica showed improvements in both the mechanical and thermal properties, viz. a $33\%$ increase in the elastic modulus and a rise in the onset degradation temperature from 355 to $371^{\circ}C$, in comparison to the Zn-ion coated structural silica.

• 공학교육연구
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• 제20권1호
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• pp.63-68
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• 2017

This research is as a case study of innovative engineering education system through idea factory of korea maritime and ocean university and deals with development of temperature-humidity control device (THCD) for fiber storage on composites in viewpoint of problem solving method. Fiber reinforced plastic (FRP) includes many variables on the composite manufacturing process. Above all, the interfacial adhesion between the fiber and the matrix acts as an important thing that decided mechanical property of the FRP, and also it is profoundly linked to external temperature and relative humidity. High void fraction leads to a result in interlaminar fracture. Therefore, in this research, to establish correlation between fiber reinforcement and fiber storage conditions of temperature and relative humidity we developed a THCD for fiber reinforcement. To evaluate performance of the THCD, glass fiber reinforced plastic (GFRP) is made under the extreme conditions each temperature $34^{\circ}C$, relative humidity 98 % and it can be said that there are the change of mechanical properties according to fiber storage conditions. As a result, the THCD showed sufficient possible application for understanding and applied research of composites field in material engineering. Also, we could check that the necessity of introduction of innovative system such as idea factory existed.

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.267-272
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• 2012

Considering the properties of the carbon nano tubes (CNT), their inclusion into the polymer matrix vastly increases the properties of the resultant composite. However, this is not the case due to the poor interfacial adhesion of the CNT and the polymer matrix. The present approach focuses on increasing the interaction between the polymer matrix and the CNT through the chemical modification of the CNT resulting in allyl ester functionalized carbon nanotubes (ACNT) and silane functionalized carbon nano tubes (SCNT) which are capable of reacting with the polymer matrix during the curing reaction. The addition of ACNT/SCNT into unsaturated polyester resin (UPR) resulted in the improvement of the electrical properties of resulted nanocomposites in comparison to the CNT. The surface resistivity, volume resistivity, dielectric strength, dry arc resistivity, and the comparative tracking index of the nanocomposites were significantly improved in comparison to CNT. The chemical modification of CNT was confirmed via spectroscopy.

• Carbon letters
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• 제15권1호
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• pp.32-37
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• 2014

Multi-walled carbon nanotube (MWCNT)/epoxy composites are prepared by a vacuum assisted resin transfer molding (VARTM) method. The mechanical properties, fracture surface morphologies, and thermal stabilities of these nanocomposites are evaluated for epoxy resins with various amounts of MWCNTs. Composites consisting of different amounts of MWCNTs displayed an increase of the work of adhesion between the MWCNTs and the matrix, which improved both the tensile and impact strengths of the composites. The tensile and impact strengths of the MWCNT/epoxy composite improved by 59 and 562% with 0.3 phr of MWCNTs, respectively, compared to the epoxy composite without MWCNTs. Thermal stability of the 0.3 phr MWCNT/epoxy composite increased compared to other epoxy composites with MWCNTs. The enhancement of the mechanical and thermal properties of the MWCNT/epoxy nanocomposites is attributed to improved dispersibility and strong interfacial interaction between the MWCNTs and the epoxy in the composites prepared by VARTM.

• 한국산학기술학회논문지
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• 제10권6호
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• pp.1298-1303
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• 2009

현무암 단섬유로 강화시킨 시멘트 복합재료의 섬유장과 혼입률에 따른 인장강도와 굽힘강도의 변화를 고찰하였다. 인장 및 굽힘강도의 증가는 섬유장의 증가에 따른 효과보다는 섬유 혼입률의 증가가 더 큰 역할을 하였다. 또한 현무암 단섬유와 시멘트 사이의 우수한 계면 접착력은 물리적 성질의 향상에 좋은 영향을 미친다고 보여진다. 시멘트의 수화시 생성되는 알칼리 조건과 유사한 포화 $Ca(OH)_2$ 용액에서의 중량감소율을 관찰한 결과 현무암 단섬유는 3주 동안의 침지 후에도 매우 작은 중량감소율을 나타냈다.